The ideal standalone Z80-based retro computer

[ladislau szilagyi]

Hi all,

please describe, in your opinion, which should be the hardware characteristics of an "ideal" standalone Z80-based retro computer!

By hardware characteristics, I mean: processor speed, RAM/EPROM size, storage media (type, storage capacity), keyboard interface, video screen interface, etc.

thanks,
Ladislau

[ladislau szilagyi]

Ok,

let me "break the ice"...

My ideal Z80 standalone computer should have:

- overclocked Z80 (20 - 25 MHz would be nice...)
- 16/32 KB EPROM (nice to have, but not a must...)
- at least 128 KB banked RAM (512 KB banked would be best)
- CF (32 MB is quite enough for me...)
- PS/2 keyboard interface
- VGA monitor interface (80 x 24 8x8 pixels chars would be best, but 64 x 48, monochrome is enough for me...)
- serial to USB ( I prefer SIO/KIO, programmable up to 112500 bauds )
- Real Time Clock
- digital I/O module, 8 leds (nice to have...)

Ladislau

[Phil G]

On Tuesday, July 25, 2023 at 12:39:28 PM UTC+1, ladislau szilagyi wrote:
> Ok,
>
> let me "break the ice"...
>
> My ideal Z80 standalone computer should have:
>
> - overclocked Z80 (20 - 25 MHz would be nice...)
> - 16/32 KB EPROM (nice to have, but not a must...)
> - at least 128 KB banked RAM (512 KB banked would be best)
> - CF (32 MB is quite enough for me...)
> - PS/2 keyboard interface
> - VGA monitor interface (80 x 24 8x8 pixels chars would be best, but 64 x 48, monochrome is enough for me...)
> - serial to USB ( I prefer SIO/KIO, programmable up to 112500 bauds )
> - Real Time Clock
> - digital I/O module, 8 leds (nice to have...)
>
> Ladislau

[Phil G]

>>please describe, in your opinion, which should be the hardware characteristics of an "ideal" standalone Z80-based retro computer!

These are my own thoughts, tongue in cheek but honest, others will likely disagree:
To me, 20-25mhz isnt retro, it doesnt give the retro experience to properly feed the nostalgia.
To be accurate, a retro Z80 should run 4mhz which was the 'industry standard' for a CP/M box, thats what we had back in the day - I enjoy Richard Russell's
CP/M music compiler, which won't run at 20mhz, its timer variables are too small.
Chipsets should be separate, ie no combinational logic, in DIP format, through-hole. All Z80 family, PIO, SIO, CTC etc. No SMD, thats not retro either.
CP/M 2.2 and 64k of ram, because thats what we had, thats what the monumental CP/M software library is based on, so that is the standard that nostalgists want to revisit.
Bytewide static ram, although expensive, was available at the time so that is good retro and much nicer than dynamic whilst allowing the nv option too.
We cant realistically have 8" drives any more - drive availability, media availability, cost, space, power - so thats one area I'd concede to modern alternative!
I think what you're describing could be termed 'modern retro' which is a different thing entirely - you asked for "an 'ideal' standalone Z80-based retro computer" :)
It all boils down to how you define 'retro' and I think we all have different ideas on that, mine is to recreate my heyday with some fidelity :)
Cheers
Phil
PS sorry I think I clicked 'post' twice...

[ladislau szilagyi]

...perhaps "The ideal standalone Z80-based homebrew computer" is a better choice... anyway, that's what I was thinking about, when I wrote the message!

Ladislau

[Douglas Miller]

On Tuesday, July 25, 2023 at 9:10:11 AM UTC-5, ladislau szilagyi wrote:
> ...perhaps "The ideal standalone Z80-based homebrew computer" is a better choice... anyway, that's what I was thinking about, when I wrote the message!
>
> Ladislau

Under the new scope of this thread, I'll just state that I have an https://www.tindie.com/products/tindiescx/sc203-modular-z180-computer-kit-for-rc2014/ and https://www.tindie.com/products/circlem/minz-u-z180-system-at-33-or-36-mhz-with-512-kb/, both of which I speak highly of. I do most of my work on simulations, but needed a modicum of real hardware for some experimentation. My SC203 has an MT011 add-on card that gives me a "smart" Ethernet adapter for CP/NET (via WizNET). Both have 512K RAM and ROM. They are Z180, but that can be (mostly) used like a Z80 from a software perspective (if you stay away from undocumented Z80 instructions).

[Roger Hanscom]

I've designed and built a couple of standalone Z80 based SBC's:

One is quite small (maybe 4.75" x 3.75"). It runs at 20 MHz with a full sixteen 8 MB "disks" on compact flash. It has two serial ports running at 115k baud (one used as a console) via a Z84C4010PEC. It uses a 128k x 8 SRAM. The two 64k x 8 halves can be accessed, but I haven't experimented with bank switching at all. It has a 32k x 8 ROM that contains a monitor, a CP/M 2.2 image, and some utilities. The ROM can be switched out of the memory map for a (roughly) 55k TPA. The most interesting part of this SBC is that it can be completely powered from the USB adapter that is the console. The downside (for some) is the use of a half dozen surface mount 74LS chips. I've collected a fair number of the old Z80 compilers and got them running (BASIC, C, PL/I, Pascal, and FORTRAN). It is amazing that these compilers that were so painful to run at 4 MHz, are *very* usable at 20 MHz!

The second is quite a bit larger (maybe 5" x 7"). Same basic features of the Z80 described above, but this one uses a Z85C30 UART for two serial ports (one used as console). It is fully through hole 74LS, and has a fully TTL compact flash interface. It can be configured for 32k or 16k banks (using a 512k x 8 SRAM), but again I have not done much with that. It has a DS1302 RTC (battery backed). It also has a native USB port based on the DLP-USB245R that is amazingly fast! Again, a monitor, CP/M 2.2 image, and a number of utilities are stored in a 32k ROM that can be switched out of the memory map.

I'd post photos of both of these Z80's, but I can't see a way to do that here.

As is usually the case, the price of function is complexity, so some of the "wish lists" posted here would possibly have to be constrained by that old adage!

Roger

[Bozo User]

On 2023-07-25, Roger Hanscom <***@gmail.com> wrote:
> I've designed and built a couple of standalone Z80 based SBC's:
>
> One is quite small (maybe 4.75" x 3.75"). It runs at 20 MHz with a full sixteen 8 MB "disks" on compact flash. It has two serial ports running at 115k baud (one used as a console) via a Z84C4010PEC. It uses a 128k x 8 SRAM. The two 64k x 8 halves can be accessed, but I haven't experimented with bank switching at all. It has a 32k x 8 ROM that contains a monitor, a CP/M 2.2 image, and some utilities. The ROM can be switched out of the memory map for a (roughly) 55k TPA. The most interesting part of this SBC is that it can be completely powered from the USB adapter that is the console. The downside (for some) is the use of a half dozen surface mount 74LS chips. I've collected a fair number of the old Z80 compilers and got them running (BASIC, C, PL/I, Pascal, and FORTRAN). It is amazing that these compilers that were so painful to run at 4 MHz, are *very* usable at 20 MHz!
>
> The second is quite a bit larger (maybe 5" x 7"). Same basic features of the Z80 described above, but this one uses a Z85C30 UART for two serial ports (one used as console). It is fully through hole 74LS, and has a fully TTL compact flash interface. It can be configured for 32k or 16k banks (using a 512k x 8 SRAM), but again I have not done much with that. It has a DS1302 RTC (battery backed). It also has a native USB port based on the DLP-USB245R that is amazingly fast! Again, a monitor, CP/M 2.2 image, and a number of utilities are stored in a 32k ROM that can be switched out of the memory map.
>
> I'd post photos of both of these Z80's, but I can't see a way to do that here.
>
> As is usually the case, the price of function is complexity, so some of the "wish lists" posted here would possibly have to be constrained by that old adage!
>
> Roger

Would a 20MHZ z80 (or more) be able to play Zmachine games (z5 and z8 version)
with enough speed? I think the 6502 on the C64 with a REU it's able to play
Z5 games with a few seconds delay and Z8 games run very slow.

You know, the interpreter to run Infocom games, but there are several
"amateur" (not so amateur since the 1993's game 'Curses!'). games to try.

Bear in mind Z3 games will run fine in any 8bit machine, but for Z8
games a 286.386, or 68k machine it's expected.

[ladislau szilagyi]

> Would a 20MHZ z80 (or more) be able to play Zmachine games (z5 and z8 version)
> with enough speed? I think the 6502 on the C64 with a REU it's able to play
> Z5 games with a few seconds delay and Z8 games run very slow.
>
> You know, the interpreter to run Infocom games, but there are several
> "amateur" (not so amateur since the 1993's game 'Curses!'). games to try.
>
> Bear in mind Z3 games will run fine in any 8bit machine, but for Z8
> games a 286.386, or 68k machine it's expected.

I'm not an expert on Z machine games... can you give me a hint about where to download some v5 or v8 games for Z80?

I suppose no color/graphics is required...

I have a 25MHz Z80 machine (Z80ALL), the screen has 64x48, it is VT52 compatible, let's give it a try :)

Ladislau

[ladislau szilagyi]

It seems no one wants to add anything, so I will disclose my favorite Z80-based stand-alone computer:

It's Bill Shen's Z80ALL. I will describe-it below:

Hardware:
- 25MHz Z80
- 128 KB RAM (4 x 32KB banks)
- KIO (2 serial 115200 bauds)
- CF
- DS1302 real time clock
- PS/2 keyboard interface
- VGA monochrome 64 x 48 8x8 pixel chars (char bit7=0: normal/1:reverse video)
- 1K font lookup table (port 0CH - 0FH)
- 3K display memory (port 0H - 0BH)
- font & display directly accessible via I/O

Software:
-can boot CP/M 2.2 or CP/M 3.0
-CP/M 2.2 software:
- 4 x 8MB disks
- xmodem works flawlessly at 115200, even with large files (hundreds of KB)
- PS/2: BIOS handles key autorepeat (useful when using a text editor, or playing a game)
- VGA: interface via BIOS is VT52 compatible ( plus video normal/reverse )
- HiTech C is enhanced (using 128KB) , therefore able to compile larger files
- Text editor TE, able to edit (in memory) files up to 64KB
- Binary editor
- WS (installed with VT52 settings)
-games:
-Tetris
-Sargon chess
-Startrek
-Backgammon
-Sokoban
-Sudoku
-Connect four
-Textfall
(more to come :)

[ladislau szilagyi]

Hi,

before receiving again complaints about my view on "retro-computers / home-brew-computers", let me explain my perspective:

In the 1970s I programmed an 8008 with its CPU clock at 400KHz (it had only a teletype-like console and punched paper tape reader); one year later, the 2MHz 8080 seemed to me super fast (it had a CRT terminal and 8 inch floppy disk); then, in the 80s, the 3.25MHz Z80 of my ZX81 was another step forward... and today I have Z80-based retro-computers with CPU clock at 7.3728MHz and 25MHz.

So, where is the "boundary"? When could one say that "X" is a "retro-computer / home-brew-computer" and "Y" is not?

In my opinion, retro computing is a hobby, a recreational activity.

Any categorization, limits or boundaries should be considered indicative and relative only.

Other, different opinions should always be acknowledged and accepted... and I will also comply with this rule of common sense.

So, please continue sharing your thoughts here about this topic...

regards,
Ladislau

[Bozo User]

On 2023-07-31, ladislau szilagyi <***@euroqst.ro> wrote:
>
>> Would a 20MHZ z80 (or more) be able to play Zmachine games (z5 and z8 version)
>> with enough speed? I think the 6502 on the C64 with a REU it's able to play
>> Z5 games with a few seconds delay and Z8 games run very slow.
>>
>> You know, the interpreter to run Infocom games, but there are several
>> "amateur" (not so amateur since the 1993's game 'Curses!'). games to try.
>>
>> Bear in mind Z3 games will run fine in any 8bit machine, but for Z8
>> games a 286.386, or 68k machine it's expected.
>
> I'm not an expert on Z machine games... can you give me a hint about where to download some v5 or v8 games for Z80?
>
> I suppose no color/graphics is required...
>
> I have a 25MHz Z80 machine (Z80ALL), the screen has 64x48, it is VT52 compatible, let's give it a try :)
>
> Ladislau
>
>

gopher://gopher.661.org
ftp://ftp.if-archive.org

Under games/zcode.

Anchor.z8 it's pretty well known, and 'Tangle.z5' (Spider and Web)
it's another good example for Z5 games.

Not for Z80, but for a Z machine interpreter. ZXZVM it's a good
example:

https://www.seasip.info/ZX/zxzvm.html

Porting hints:

https://www.seasip.info/ZX/zxzvmport.html

[Douglas Miller]

I mostly lean towards Phil's definition of "retro", but that's just opinion. I will say that CP/M 3, MP/M, and CP/NET were all viable products back in the day, and so building systems designed for them is still retro. More (banked) RAM, and "smart" network controllers were in existence. The problem with floppies in the modern world might make me allow an exception for disk, using CF or SDCard - at the loss of the valuable experience of swapping floppies and trying to fit things in tiny spaces.

Things like PS/2 keyboards and VGA are not, in my opinion, "retro" but they also place a heavier burden on the software on a Z80. As systems evolved into 16-bit, 32-bit, and now 64-bit, with faster and faster clocks and more directly-addressable RAM, the hardware also evolved to take advantage of the extra resources. These peripherals really weren't intended for a 4MHz 8-bit CPU and a 64K address space. Having never tried to integrate these into CP/M, it's just my impression. But it seems you either need to bank-out the ROM routines (like RomWBW - which might not fall into this definition of retro) or else bank-out the BIOS (like CP/M 3 or some systems that had a ROM BIOS), else you end up losing more of the precious 64K address space to software overhead. It obviously can be done, but there are costs.

[Adam Sampson]

ladislau szilagyi <***@euroqst.ro> writes:

> please describe, in your opinion, which should be the hardware
> characteristics of an "ideal" standalone Z80-based retro computer!

It would be nice to have a banking scheme that works well both for MP/M
and FUZIX, and serial ports that are capable of running reliably at high
speeds (115200+ baud).

--
Adam Sampson <***@offog.org> <http://offog.org/>

[Udo Munk]

Adam Sampson schrieb am Dienstag, 25. Juli 2023 um 20:45:04 UTC+2:
> It would be nice to have a banking scheme that works well both for MP/M
> and FUZIX, and serial ports that are capable of running reliably at high
> speeds (115200+ baud).

See z80pack cpmsim memory implementation, works with CP/M 3, MP/M and Fuzix.

A serial port runnig at 115kbaud lets the Z80 @ 4 MHz service that and nothing else
anymore. Even with a larger buffer the Z80 gets overrun if it is running some OS besides
this serial port.

[ladislau szilagyi]

Any banked RAM memory with total size > 64KB (2 x 64K, 4 x 32K, 32 x 16K, etc.) should be fully used, even with CP/M 2.2

See https://github.com/Laci1953/RC2014-CPM/tree/main/te (text editor - all edited text is stored in RAM)

or https://github.com/Laci1953/HiTech-C-compiler-enhanced (all available RAM is used to allocate objects used by the compiler)

Of course, you need a small piece of software to move bytes from/to CP/M's 64KB to/from extra RAM banks, and a memory allocator... but these components can be made.

The gain is significant (larger files can be edited, or compiled) , of course with a small price paid as a reduction of processing speed.

I know (and in this thread there are already some cases) a lot of homebrew Z80 computers having large RAM storage spaces, but using only 64KB, because "CP/M 2.2 can use only 64KB" ... what a waste of resources!

It's just an opinion...

[yeti]

My ideal Z80 system would run CP/M (other OSs optional) and would not
need a PC nanny.

It should be able to build all it's software and firmware (EPROM, flash,
micro-controllers) itself and even able to flash/program the
needed parts.

Speed is not my priority. It's ok if some things are slow and an
optional(!) PC-nanny would be used as turbocharger, but it just should
be possible for my dream system to reproduce itself completely without
that nanny from outer space.

I'm not against helper chips like seen in Z80-MBC(1/2/3). But there
probably never will be a compiler for them on CP/M and I cannot imagine
seeing more than an assembler for such helpers soon. But if the
firmware for such helpers were only need an assembler, it'd be perfect.

2nd best: Maybe even the firmware in such a helper chip could be treated
as a constant, but then at least duplicating that into an empty helper
MCU for the next build of such a system should be doable using the
existing system.

If using SD as storage, it should be able to format these on its own
too.

...

You get the idea...

And I miss removable media. Everything on one fat FAT-FS SD induces its
own limits. It'd be ok if that were hot swapable 8 Meg "disks" provided
by SPI flash chips (25Qxyz) attached via robust DB9 connectors. Maybe
someone has a better idea?

Just dreaming...

--
Take Back Control! -- Mesh The Planet!
I do not play Nethack, I do play GNUS! o;-)
Solid facts do not need 1001 pictures.

[Zbig]

What do you think about this one: https://www.thebyteattic.com/p/agon.html
Is it close to your ideal?
And here's CP/M 2.2 for the machine: https://github.com/nihirash/Agon-CPM2.2

[ladislau szilagyi]

Pe sâmbătă, 19 august 2023, la 20:47:10 UTC+3, Zbig a scris:
> What do you think about this one: https://www.thebyteattic.com/p/agon.html
> Is it close to your ideal?
> And here's CP/M 2.2 for the machine: https://github.com/nihirash/Agon-CPM2.2

It is a ez80 computer, not a Z80 one...

[Zbig]

> It is a ez80 computer, not a Z80 one...

eZ80 has two modes of operaion: Z80 mode and eZ80 ADL mode (ADL Mode is offered to provide code execution time that is four times faster than that of a standard Z80 CPU operating at the same clock speed).

So you can operate it in its Z80 mode.

[ladislau szilagyi]

Pe duminică, 20 august 2023, la 11:19:30 UTC+3, Zbig a scris:

> eZ80 has two modes of operaion: Z80 mode and eZ80 ADL mode (ADL Mode is offered to provide code execution time that is four times faster than that of a standard Z80 CPU operating at the same clock speed).
> So you can operate it in its Z80 mode.

Ok, I agree that eZ80 can operate in Z80 mode, but, how about some other hardware items that are Z80 compatible, and can even run CP/M ?

Some examples:

- ZMOB, a 256 node Z80A cluster designed and built at University of Maryland as part of NASA NSG-7253. That's a total of 1GHz of Z80 power. See https://www.ijcai.org/Proceedings/81-2/Papers/071.pdf

- Papillo Pro FPGA board running Will Sowerbutts 'SocZ80' FPGA firmware - T80 core @ 128Mhz. See https://sowerbutts.com/socz80/

Well, in my opinion, in this thread we should discuss only about standalone retro/homebrew computers provided with the Z80 CPU.
The "real" Z80 (Z84C00) or its "clones" (e.g. MK3880, LH0080, U880, MMN80CPU, ...) , with clock frequencies up to 20MHz.
Not Z180/Z280/Z800/R800/eZ80 ...

Just my opinion...

Ladislau

[Zbig]

> Ok, I agree that eZ80 can operate in Z80 mode, but, how about some other hardware items that are Z80 compatible, and can even run CP/M ?

Yes, it can run CP/M as I already noted; there's a CP/M 2.2 prepared for Agon Light.

> Well, in my opinion, in this thread we should discuss only about standalone retro/homebrew computers provided with the Z80 CPU.

Yes, its CPU can be seen as a „superset” of „ordinary” Z80 CPU.

> The "real" Z80 (Z84C00) or its "clones" (e.g. MK3880, LH0080, U880, MMN80CPU, ...) , with clock frequencies up to 20MHz.
> Not Z180/Z280/Z800/R800/eZ80 ...

Why not?
If ran under CP/M control „Agon Light” uses its CPU exactly as Z80,
because CP/M couldn't be run otherwise (ADL is different mode of
operation).

If you — for some particular reason, or for no reason at all — don't like
Bernardo's design, I can' help it, of course. Just a quick reminder, that
not so long ago someone recommended a few posts earlier:

„Any categorization, limits or boundaries should be considered indicative and relative only.

Other, different opinions should always be acknowledged and accepted... and I will also comply with this rule of common sense.”

Maybe you know, who was that? :)

[Zbig]

> The "real" Z80 (Z84C00) or its "clones" (e.g. MK3880, LH0080, U880, MMN80CPU, ...) , with clock frequencies up to 20MHz.
> Not Z180/Z280/Z800/R800/eZ80 ...

You know, it sounds kind of like: „the only real processor
for PC is 8086/88 with clock frequencies up to 8 MHz —
not 80286. 80386, 80486, Pentium…”. ;)

[ladislau szilagyi]

I really apologize,

it's my mistake, because of my insufficient knowledge of the English language...

I was 100% convinced that "Z80-based" is different from "Z80-compatible"... it turns out not!

I'm sorry for the misunderstanding, it's never late to improve my skills in mastering the English language!

So, in the end, I learned something remarkable: RC2014 is a good example of an "8080-based" retro computer...

Ladislau

[Zbig]

I'm seriously afraid that irony attempt won't be of much help here.

— RC2014 uses Z80 as Z80; not as i8080 — is it correct?
— Agon Light (when controlled by CP/M) uses eZ80 as… Z80,
not as eZ80 — is it correct?

Unless, of course, you wanted to say something (using an analogy):
„I don't care about PCs with AMD inside — I respect only Intel
processors, and not later than 8088, and not faster than 8 MHz“

In other words: if you don't want to talk about „The ideal standalone
Z80-based retro computer” — it was better idea to name this thread
„Bill Shen's Z80ALL” — which is fine design, of course.
But there are other fine designs also available…

https://www.youtube.com/watch?v=13zfEc67oYU

[ladislau szilagyi]

Ok, why don't you open a new conversation, with the title "The ideal standalone Z80-compatible retro/homebrew computer" ?

AgonLight is fit to be presented there...

Ladislau

[Zbig]

> Ok, why don't you open a new conversation, with the title "The ideal standalone Z80-compatible retro/homebrew computer" ?
>
> AgonLight is fit to be presented there...

AgonLight is also fit to be presented here.

Consider one more example: in former East Germany they manufactured
Z80 clone named U880. So you would exclude the machine fitted with U880
from this thread, because its CPU didn't have proud „Z80” print on its package?

I thought you were serious by stating:

”different opinions should always be acknowledged and accepted... and
I will also comply with this rule of common sense”

It seems I was wrong.

But OK, then leaving this thread to not bother you with different opinion. Bye!

[dxforth]

On 21/08/2023 8:11 pm, Zbig wrote:
>> Ok, why don't you open a new conversation, with the title "The ideal standalone Z80-compatible retro/homebrew computer" ?
>>
>> AgonLight is fit to be presented there...
>
> AgonLight is also fit to be presented here.
>
> Consider one more example: in former East Germany they manufactured
> Z80 clone named U880. So you would exclude the machine fitted with U880
> from this thread, because its CPU didn't have proud „Z80” print on its package?
>
> I thought you were serious by stating:
>
> ”different opinions should always be acknowledged and accepted... and
> I will also comply with this rule of common sense”
>
> It seems I was wrong.
>
> But OK, then leaving this thread to not bother you with different opinion. Bye!

"please describe, in your opinion, which should be the hardware characteristics of
an "ideal" standalone Z80-based retro computer!"

I never heard of the Agon Light until you mentioned it. It's the only one that
got me interested enough to investigate it. So thanks for that.

[ladislau szilagyi]

> >
> > Consider one more example: in former East Germany they manufactured
> > Z80 clone named U880. So you would exclude the machine fitted with U880
> > from this thread, because its CPU didn't have proud „Z80” print on its package?
> >

@Zbig:

I wonder if you are really reading my messages, or only responding because you need to respond...
If you read more carefully my past messages, you would have noticed that I mentioned, in my 20 august message, this statement:

"Well, in my opinion, in this thread we should discuss only about standalone retro/homebrew computers provided with the Z80 CPU.
The "real" Z80 (Z84C00) or its "clones" (e.g. MK3880, LH0080, U880, MMN80CPU, ...) , with clock frequencies up to 20MHz.
Not Z180/Z280/Z800/R800/eZ80 ... "

There is an U880 clearly mentioned here... and you know why? Because I worked in the 80's with some East Germany manufactured computers... what about your past experiences related to East European Z80-based computers? Bulgarian, East-German, Romanian, Russian... ( I wrote real-time operating systems for Romanian computers... ).

But, it seems you are not really interested in the facts I mentioned, because you are targeting only one goal: "I am right, and you are wrong!"

As for AgonLight, see here: https://groups.google.com/g/retro-comp/c/nGfo3iKdZkY an opinion...

There are Pros, but also Cons...

But, again, in this conversation, in my opinion, we should talk only about Z80-based (NOT Z80-compatible) retro/homebrew computers.

My view on the terms Z80 & Z80-compatible is the following:

Z80 = "real" Z80 (Z84C00) or its "clones" (e.g. MK3880, LH0080, U880, MMN80CPU, ...)
Z80-compatible = Z180/Z280/Z800/R800/eZ80 (...and others)

Once again, as I already said:

"In my opinion, retro computing is a hobby, a recreational activity.
Any categorization, limits or boundaries should be considered indicative and relative only.
Other, different opinions should always be acknowledged and accepted... and I will also comply with this rule of common sense.
So, please continue sharing your thoughts here about THIS topic..."

The current topic is "standalone Z80-based retro/homebrew computers".
NOT "standalone Z80-compatible retro/homebrew computers"

Please, if some of you want to debate issues regarding "Z80-compatible retro/homebrew computers", or any other topic different from "Z80-based retro/homebrew computers", please do open a new Conversation, with an appropriate title, because I will not waste any more time responding to out-of-topic messages.

Ladislau

[Tadeusz Pycio]

Ladislau has a lot of things right, Z80 based is not the same as Z80 compatible. Compatibility is a term that covers a broader spectrum, there can be Z80, "Super-Z80" like Z180, Z280, eZ80, hardware emulations on FPGA and software emulations on any other architecture.
Returning to the topic of the thread, I believe that there is no perfect Z80 computer, each has its limitations related to its purpose. You will need a different set up when you want to play games, a different set up to run CP/M, as well as a different set up to run MP/M. The low performance of the processor does not allow to build a universal computer as we know it from modern PCs. Yes, you can attempt to build one, but it will be a difficult task and quite expensive if you want to use chips from that era. I believe that any system running at a clock greater than 6MHz will give you a comfortable working environment with CP/M. Remember - the ZX Spectrum ran at 3.5MHz and provided a lot of entertainment.

[dxforth]

On 22/08/2023 7:34 pm, Tadeusz Pycio wrote:
> Ladislau has a lot of things right, Z80 based is not the same as Z80 compatible. Compatibility is a term that covers a broader spectrum, there can be Z80, "Super-Z80" like Z180, Z280, eZ80, hardware emulations on FPGA and software emulations on any other architecture.

If 'Z80 based' is to mean 'Z80 only' it rules out the vast majority of
modern designs. For designers attractiveness lies is the possibility
of doing *more* than what was done 40 years ago. If what's offered now
not only gives better performance but is also designed to be backward
compatible, who wouldn't be interested? Let's not forget the Z80 itself
was a new processor built upon an old design and became popular for
that reason.

[Tadeusz Pycio]

Why do you think it excludes most new projects? This year I designed two RCBus modules using the Z80. Also, a module on the Z280 supported by a contemporary AVR microcontroller was also created. One may wonder if such solutions can be called "retro", but certainly the Z80 modules are based on the Z80, and the Z280 is a Z80-compatible processor. The whole charm of such solutions lies in the use of technology from that period. A few years ago I designed a Z80 emulator running under CP/M, using all the modern advances on an ARM Cortex-M3 processor, and abandoned it because for me it was a dead end. I believe that the choice of components is an individual designer's choice and any solution is good, whether on Z80 or FPGA. Some will consider it right, others will question the sense of using a 1976 processor or using a GHz programmable array.

[Zbig]

> Why do you think it excludes most new projects? This year I designed two
> RCBus modules using the Z80. Also, a module on the Z280 supported by
> a contemporary AVR microcontroller was also created. One may wonder
> if such solutions can be called "retro", but certainly the Z80 modules are
> based on the Z80, and the Z280 is a Z80-compatible processor.

I don't want to disturb anyone with my „different opinion” — so
the last word here. And actually it's not my word — but the word
of eZ80 creators and manufacturers. In the PDF document they released
they clearly stated:

„The eZ80™ is ZiLOG’s next-generation Z80™ processor. The eZ80 provides 16
times the performance of a traditional Z80. The multiple operating modes of the
processor allows Z80 and Z180 code to be run without change in the same appli-
cation with new code [..] At the same time, the eZ80 remains 100% Z80 code-compat-
ible, reducing customer development time. [..]
Z80 High-Performance Microprocessor Core. The eZ80 is one of the fastest 8-
bit CPUs available today, executing code 4 times faster than a standard Z80 oper-
ating at the same clock speed. [..]
The eZ80 is ZiLOG’s fourth-generation Z80 processor core.”

I could quote even more — but I believe it's quite enough. So the creators themselves
call eZ80 simply „next-generation Z80”, but you and Ladislau „know better”.

BTW: as I've found out, DDR-manufactured U880 wasn't actually exact clone of Z80:
„The U880 is an unlicensed clone of the Zilog Z80 microprocessor, also supporting
illegal opcodes and bugs, except for very minor differences like not setting the CY
flag for the OUTI command (when L goes zero).” — so you would include that one
into your list — although it was merely 99% compatible, at most — and you're willing
to exclude „next-generation Z80” (which hasn't such issues) only because it's newer?
Then maybe 8 Mhz clocked Z80 also should be excluded?

OK, „over and out”.

[Tadeusz Pycio]

How do I understand "know better"? You think the eZ80 is the only right choice, then so be it, it is your opinion and I don't necessarily have to agree with it. The AgonLight is a great computer, but it is not the only right choice for Z80 supporters. The discussion is starting to resemble direct marketing - either AgonLight with eZ80 or you don't know. Everyone has different expectations from such a system and everyone can find what suits them. The performance argument does not appeal to me, there are definitely faster processors being produced nowadays and costing far less. If I want to play with something modern, I will make a flashing LED on RISC-V for $0.1 ;-)

[Zbig]

> How do I understand "know better"? You think the eZ80 is the only right choice, then so be it,

You've completely missed the point; you may want to read again,
what I wrote — but this time SLOWLY AND WITH UNDERSTANDING.

Cheers! :)

[[e-mail]]

On Tuesday, 22 August 2023 at 13:56:30 UTC+1, Tadeusz Pycio wrote:
> How do I understand "know better"? You think the eZ80 is the only right choice, then so be it, it is your opinion and I don't necessarily have to agree with it. The AgonLight is a great computer, but it is not the only right choice for Z80 supporters. The discussion is starting to resemble direct marketing - either AgonLight with eZ80 or you don't know. Everyone has different expectations from such a system and everyone can find what suits them. The performance argument does not appeal to me, there are definitely faster processors being produced nowadays and costing far less. If I want to play with something modern, I will make a flashing LED on RISC-V for $0.1 ;-)

In my mind (in the context of 8080/z80 etc) , a computer is only a great computer if it supports CP/M 3 as well as CP/M 2.2 to take advantage of the extra horsepower, if it has those beefy chips like eZ80. The CP/M 3 disk buffering is advantageous. I'm not aware it is implemented on AgonLight yet.
And it becomes truly great when RomWBW runs on it.

Richard

[dxforth]

On 22/08/2023 9:44 pm, Tadeusz Pycio wrote:
> Why do you think it excludes most new projects? This year I designed two RCBus modules using the Z80. Also, a module on the Z280 supported by a contemporary AVR microcontroller was also created. One may wonder if such solutions can be called "retro", but certainly the Z80 modules are based on the Z80, and the Z280 is a Z80-compatible processor. The whole charm of such solutions lies in the use of technology from that period.

The ez80 is obviously compatible too. I'm not a collector of retro hardware. The charm
for me is the software of that period. Software small enough that anyone can grasp it.
What I never care for were the hardware limitations - the slow CPUs and disk drives.
I've little hankering to spend several hundred dollars on a backplane of 'Z80' cards to
recreate a slow vanilla CP/M system I owned 35 years ago. I still enjoy developing
software on CP/M which is why I won't do it on ancient hardware. If it were just about
CP/M then I'd hardly need an Agon Lite board. In addition to the ez80's better speed,
there's a new OS and video opportunities for retro Z80 language enthusiasts to play with.
Granted it's early days. What's less likely is the project getting this far had it been
a stock Z80 under the hood.

[Tadeusz Pycio]

Why spend the money then? Nowadays, there are excellent PC emulators that far outperform any Z80-compatible hardware solution. If we feel the need for separate hardware, we can emulate the entire CP/M environment on an inexpensive ESP32, which can also be found on AgonLite, using the RunCPM project. In each of these examples, we can enjoy convenience and performance. What distinguishes these solutions from the typical "slow" modular Z80 system is the lack of expandability. It is a closed system, with no freedom to add any extensions. Therefore, for me personally, there is no difference between closed hardware solutions and emulators, and if I had to choose between the two, I would prefer the emulator (which I often use when I don't have access to my hardware).

[dxforth]

On 23/08/2023 4:41 am, Tadeusz Pycio wrote:
>
> Why spend the money then? Nowadays, there are excellent PC emulators that far outperform any Z80-compatible hardware solution.

I'm still looking for that 'excellent' MS-DOS emulator (which I'll use with MYZ80)
that conveniently interfaces with Windows.

> If we feel the need for separate hardware, we can emulate the entire CP/M environment on an inexpensive ESP32, which can also be found on AgonLite, using the RunCPM project. In each of these examples, we can enjoy convenience and performance. What distinguishes these solutions from the typical "slow" modular Z80 system is the lack of expandability. It is a closed system, with no freedom to add any extensions.

If hardware control is really of interest, there's Arduino where the add-ons are
cheap, prolific and easier to program due to the pre-written routines, large
knowledge and user base.

Whether I'd run CP/M on the Agon is questionable. The latter is closer to the
likes of Amstrad and Spectrum and where I see any development happening.

[Chris Syntichakis]

On Wednesday, 23 August 2023 at 07:10:31 UTC+1, dxforth wrote:
> I'm still looking for that 'excellent' MS-DOS emulator (which I'll use with MYZ80)

try this http://www.vdosplus.org/

[dxforth]

On 25/08/2023 4:37 pm, Chris Syntichakis wrote:
> On Wednesday, 23 August 2023 at 07:10:31 UTC+1, dxforth wrote:
>> I'm still looking for that 'excellent' MS-DOS emulator (which I'll use with MYZ80)
>
> try this http://www.vdosplus.org/

Thanks. MYZ80 boots on it but doing anything cause a crash e.g. DIR gives me a
page then freezes. Original DOSBOX has its quirks but generally works.

[Chris Syntichakis]

On Friday, 25 August 2023 at 11:39:15 UTC+1, dxforth wrote:
> On 25/08/2023 4:37 pm, Chris Syntichakis wrote:
> > On Wednesday, 23 August 2023 at 07:10:31 UTC+1, dxforth wrote:
> >> I'm still looking for that 'excellent' MS-DOS emulator (which I'll use with MYZ80)
> >
> > try this http://www.vdosplus.org/
> Thanks. MYZ80 boots on it but doing anything cause a crash e.g. DIR gives me a
> page then freezes. Original DOSBOX has its quirks but generally works.

I know I am OOT, but, there is another MSDOS 'emulator' for x64 windows..

http://takeda-toshiya.my.coocan.jp/ has an MSDOS player (an .exe that runs old MSDOS .exe)
There is a CP/M player as well there.
HTH

[Zbig]

> If hardware control is really of interest, there's Arduino where the add-ons are
> cheap, prolific and easier to program due to the pre-written routines, large
> knowledge and user base.

Not only that; AmForth and Flashfort work even on little ATmega328P
(the one in Arduino Uno) just fine — and AVR's assembly language
resembles to some extent the one of 8080/Z80:
http://www.avr-asm-tutorial.net/avr_en/micro_beginner/instructions.html

[dxforth]

On 28/08/2023 1:48 am, Zbig wrote:
>> If hardware control is really of interest, there's Arduino where the add-ons are
>> cheap, prolific and easier to program due to the pre-written routines, large
>> knowledge and user base.
>
> Not only that; AmForth and Flashfort work even on little ATmega328P
> (the one in Arduino Uno) just fine — and AVR's assembly language
> resembles to some extent the one of 8080/Z80:
> http://www.avr-asm-tutorial.net/avr_en/micro_beginner/instructions.html

Even if one isn't immediately attracted, it's amazing how 'cheap and prolific'
grows on one. In some ways Arduino/AVR was too successful as it got the
attention of chip counterfeiters.

[Zbig]

> Why spend the money then? Nowadays, there are excellent PC emulators that far outperform any Z80-compatible hardware solution.

Surely you never heard of Low Fat Computing.

> Therefore, for me personally, there is no difference between closed hardware solutions and emulators, and if I had
> to choose between the two, I would prefer the emulator

Agon Light is open-sourced both hardware and software.

[[e-mail]]

On Tuesday, August 22, 2023 at 2:41:45 PM UTC-4, Tadeusz Pycio wrote:
> Why spend the money then? Nowadays, there are excellent PC emulators that far outperform any Z80-compatible hardware solution. If we feel the need for separate hardware, we can emulate the entire CP/M environment on an inexpensive ESP32, which can also be found on AgonLite, using the RunCPM project. In each of these examples, we can enjoy convenience and performance. What distinguishes these solutions from the typical "slow" modular Z80 system is the lack of expandability. It is a closed system, with no freedom to add any extensions. Therefore, for me personally, there is no difference between closed hardware solutions and emulators, and if I had to choose between the two, I would prefer the emulator (which I often use when I don't have access to my hardware).

But the emulators are not "closed" -- I added AM9511 to RunCPM and other emulators. And, other bits and bobs can be added. I do use an "Altair-Duino" for the blinking lights -- yes, I used an Altair back in the day, but really prefer the smaller Altair-Duino. Part of the charm (for me) _is_ the speed (rather the lack thereof) Between 2Mhz and 64K, I think I have all the old-timey bases covered.

I really don't understand the urge to "push" a Z80 to 20, 50, 100Mhz and 128KB, 4MB of memory. The fun is the lack of memory and lack of speed (for me). I have been contemplating getting an old-timey ASR-33 teletype and an old-timer cassette recorder for the "real feeling". If I actually need to run a word processor, I *could* do most of what I need with WordStar 3.3, but I need to use Microsoft 365, Google Docs, etc. to actually collaborate with others (with a side of OpenOffice). Doesn't actually add that much, but it informs that the bulk of computing has been to make it accessible.

So, what is the "perfect Z80" for me? 32k to 128k of RAM, clock from 2 to 6MHz, serial ports (up to 38400 baud). CP/M 2.2 or 3, with VT52 terminal (for maximum WordStar 3.3 compatibility -- note that ANSI terminals cannot run SpelStar properly! -Real VT100s can be coerced),

Tek 4100 for graphics, Diablo 630 for text printing.

128K of memory does allow for a bit of bank-switching, which is useful for MP/M. I would want a 56/8 switching configuration. Or 56/4/4. Since I use and write software for CP/M 2.2, I don't need much beyond that. As to speed? 2Mhz is ok; same as the old Altair, 4Mhz was a standard for a bit, and 6MHz always felt lie "turbo" to me. If I need more, I just use a modern system.

I love the blinking lights of the Altair / Altair-Duino -- warm and comfortable. My Altar-Duino lives just under my 34" Ultrawide LG monitor. Usually running "kill-the-bit" or some such for visual amusement as I am working.

[Roger Hanscom]

On Saturday, August 26, 2023 at 9:40:50 AM UTC-7, ***@gmail.com wrote:

I agree with most of what you posted, but ...

> I really don't understand the urge to "push" a Z80 to 20, 50, 100Mhz and 128KB, 4MB of memory.

I like to fool around with the old compilers (C, FORTRAN, PL/I, etc.). At 4 MHz, using them can be quite painful. So that is why I built myself a very small Z80 SBC (roughly 4.5" x 4") that runs at 20 MHz and can be powered from the USB port that acts as the console (at 115k baud). It uses a stock CMOS Zilog CPU and SIO, runs CP/M 2.2, and has a compact flash interface that provides sixteen 8 MB "disks". I'd post a photo, but I don't see any way to do that here. It has 32k of EEPROM and 128k of SRAM. I suppose that would support some sort of bank switching, but I've not experimented with that nor have I seen the need to do that .... just yet. The second serial port of the SIO is available for other serial devices. All of the legacy CP/M software that I like to use fits on this little speed demon, and provides a *very* comfortable and responsive CP/M environment!

Roger

[Zbig]

> So, what is the "perfect Z80" for me? 32k to 128k of RAM, clock from 2 to 6MHz, serial ports (up to 38400 baud). CP/M 2.2 or 3, with VT52 terminal (for maximum WordStar 3.3 compatibility -- note that ANSI terminals cannot run SpelStar properly! -Real VT100s can be coerced),

Then you'll love good old Commodore 128 in its CP/M mode: running at 2 MHz, 128 kB, CP/M 3, Wordstar of course can be run etc. Everything as you wish.

[dxforth]

On 27/08/2023 9:03 am, Zbig wrote:
>
> Then you'll love good old Commodore 128 in its CP/M mode: running at 2 MHz, 128 kB, CP/M 3, Wordstar of course can be run etc. Everything as you wish.

Not for me. Even a 4MHz Z80 with regular disk drives would feel like purgatory
at this point of time. Not even sure I could manage a 'standalone' computer any
more.

[Greg Holdren]

On Saturday, August 26, 2023 at 9:40:50 AM UTC-7, ***@gmail.com wrote:

>
> I really don't understand the urge to "push" a Z80 to 20, 50, 100Mhz and 128KB, 4MB of memory. The fun is the lack of memory and lack of speed (for me). I have been contemplating getting an old-timey ASR-33 teletype and an old-timer cassette recorder for the "real feeling". If I actually need to run a word processor, I *could* do most of what I need with WordStar 3.3, but I need to use Microsoft 365, Google Docs, etc. to actually collaborate with others (with a side of OpenOffice). Doesn't actually add that much, but it informs that the bulk of computing has been to make it accessible.
>

The 20MHz Z80 will do 20MHz without pushing. :)

Greg

[Jeff Jonas]

> Let's not forget the Z80 itself was a new processor
> built upon an old design and became popular for that reason.

Yes, no, kinda, maybe?
8080 compatibility definitely helped on the software side,
running CP/M and such.

But the Z80's hardware was tremendously easier to use,
almost like silicon-chip Lego, thus becoming the favorite for embedded systems
such as "smart modems", SCSI controllers, terminal servers.
In a way, the Z80 peripherals were "the tail wagging the dog"
because they were so popular, particularly the SIO dual-channel serial I/O chips.

Z80 hardware features:

+5 volts only, no +/- 12v

single phase clock: no special clock generator required

Z80 native peripheral chips self-arbitrated DMA and vectored interrupts via daisy-chain.
No interrupt controller required.

built in dram refresh cycle, making RAM interfacing easier.

The Z80 signals were so direct and easy to use
that they formed the basis of the STD bus (which was later extended).

I/O address space was separate from the 64k memory address space
due to IN, OUT instructions asserting the /IORQ signal instead of /MREQ

and other things :-)

--

[Jeff Jonas]

> Let's not forget the Z80 itself was a new processor
> built upon an old design and became popular for that reason.

Yes, no, kinda, maybe?
8080 compatibility definitely helped on the software side,
running CP/M and such.

But the Z80's hardware was tremendously easier to use,
almost like silicon-chip Lego, thus becoming the favorite for embedded systems
such as "smart modems", SCSI controllers, terminal servers.
In a way, the Z80 peripherals were "the tail wagging the dog"
because they were so popular, particularly the SIO dual-channel serial I/O chips.

Z80 hardware features:

+5 volts only, no +/- 12v

single phase clock: no special clock generator required

Z80 native peripheral chips self-arbitrated DMA and vectored interrupts via daisy-chain.
No interrupt controller required.

built in dram refresh cycle, making RAM interfacing easier.

The Z80 signals were so direct and easy to use
that they formed the basis of the STD bus (which was later extended).

I/O address space was separate from the 64k memory address space
due to IN, OUT instructions asserting the /IORQ signal instead of /MREQ

and other things :-)

--

[dxforth]

On 7/09/2023 1:50 pm, Jeff Jonas wrote:
>> Let's not forget the Z80 itself was a new processor
>> built upon an old design and became popular for that reason.
>
> Yes, no, kinda, maybe?
> 8080 compatibility definitely helped on the software side,
> running CP/M and such.
>
> But the Z80's hardware was tremendously easier to use,
> almost like silicon-chip Lego, thus becoming the favorite for embedded systems
> such as "smart modems", SCSI controllers, terminal servers.
> In a way, the Z80 peripherals were "the tail wagging the dog"
> because they were so popular, particularly the SIO dual-channel serial I/O chips.
>
> Z80 hardware features:
>
> +5 volts only, no +/- 12v
>
> single phase clock: no special clock generator required
>
> Z80 native peripheral chips self-arbitrated DMA and vectored interrupts via daisy-chain.
> No interrupt controller required.
>
> built in dram refresh cycle, making RAM interfacing easier.
>
> The Z80 signals were so direct and easy to use
> that they formed the basis of the STD bus (which was later extended).
>
> I/O address space was separate from the 64k memory address space
> due to IN, OUT instructions asserting the /IORQ signal instead of /MREQ
>
> and other things :-)

I worked in telecom. Equipment originating from Europe (Siemens) tended to
use the 8085 while the Japanese (Ando) used the Z80. So not a great deal
of difference between them in that market. Unlike Zilog, Intel appears
to have lost interest in the 8080 line. I wasn't aware the 8085's 'undoc'
instructions were actually new instructions which Intel, in their wisdom,
chose to disown.

[pH]

On 2023-09-07, dxforth <***@gmail.com> wrote:
> On 7/09/2023 1:50 pm, Jeff Jonas wrote:
>>> Let's not forget the Z80 itself was a new processor
>>> built upon an old design and became popular for that reason.
>>
>> Yes, no, kinda, maybe?
>> 8080 compatibility definitely helped on the software side,
>> running CP/M and such.
>>
>> But the Z80's hardware was tremendously easier to use,
>> almost like silicon-chip Lego, thus becoming the favorite for embedded systems
>> such as "smart modems", SCSI controllers, terminal servers.
>> In a way, the Z80 peripherals were "the tail wagging the dog"
>> because they were so popular, particularly the SIO dual-channel serial I/O chips.
>>
>> Z80 hardware features:
>>
>> +5 volts only, no +/- 12v
>>
>> single phase clock: no special clock generator required
>>
>> Z80 native peripheral chips self-arbitrated DMA and vectored interrupts via daisy-chain.
>> No interrupt controller required.
>>
>> built in dram refresh cycle, making RAM interfacing easier.
>>
>> The Z80 signals were so direct and easy to use
>> that they formed the basis of the STD bus (which was later extended).
>>
>> I/O address space was separate from the 64k memory address space
>> due to IN, OUT instructions asserting the /IORQ signal instead of /MREQ
>>
>> and other things :-)
>
> I worked in telecom. Equipment originating from Europe (Siemens) tended to
> use the 8085 while the Japanese (Ando) used the Z80. So not a great deal
> of difference between them in that market. Unlike Zilog, Intel appears
> to have lost interest in the 8080 line. I wasn't aware the 8085's 'undoc'
> instructions were actually new instructions which Intel, in their wisdom,
> chose to disown.

What about Steve Ciarcia's (sp?) SB180 single board computer as featured in
Byte Magazine (before it's demise). He had a column called "Circuit
Cellar", I think.

As I recall, though, it used a Hitachi chip of some sort rather than a Z80.

Well, CP/M faded from the scene far too early in my opinion, but I still use
jstar to satisfy my WordStar finger memory from thsoe days.

pH in Aptos

[yeti]

pH <***@gmail.org> writes:

> What about Steve Ciarcia's (sp?) SB180 single board computer as
> featured in Byte Magazine (before it's demise). He had a column
> called "Circuit Cellar", I think.
>
> As I recall, though, it used a Hitachi chip of some sort rather than a
> Z80.

This one?

<https://archive.org/details/BYTE_Vol_10-09_1985-09_10th_Anniversary_Issue>

--
This stealth signature intentionally left blank.

[pH]

On 2023-09-07, yeti <***@tilde.institute> wrote:
> pH <***@gmail.org> writes:
>
>> What about Steve Ciarcia's (sp?) SB180 single board computer as
>> featured in Byte Magazine (before it's demise). He had a column
>> called "Circuit Cellar", I think.
>>
>> As I recall, though, it used a Hitachi chip of some sort rather than a
>> Z80.
>
> This one?
>
><https://archive.org/details/BYTE_Vol_10-09_1985-09_10th_Anniversary_Issue>
>

That sure looks to be the animal...wow, thanks for the link!
pH

[Roger Hanscom]

On Thursday, September 7, 2023 at 9:03:26 AM UTC-7, pH wrote:
....<snip>......
> What about Steve Ciarcia's (sp?) SB180 single board computer as featured in
> Byte Magazine (before it's demise). He had a column called "Circuit
> Cellar", I think.

Correct on all counts! The Ciarcia SBC was based on the Hitachi Z180. IMO, the Z180 is not a good example of a "z80 based" CPU. It broke the I/O opcodes that used the content of the C register to address ports. There was a good reason for that (too detailed to go into here), but unfortunately those opcodes were used in a lot of legacy Z80 applications. It was a nifty way to address multiple I/O ports just by changing the content of C. In order to run those old Z80 applications on a Z180, the parts of the code that used those opcodes had to be rewritten.

The claim was that the Z180 was 100% binary code compatible with the Z80 was obviously not true, and that might have been a factor in the lack of popularity of that CPU? It certainly never achieved the same level of acceptance as the venerable Z80! BTW, that same "glitch" might exist in the eZ80 as well. I just don't know.

Roger

[pH]

On 2023-09-08, Roger Hanscom <***@gmail.com> wrote:
> On Thursday, September 7, 2023 at 9:03:26 AM UTC-7, pH wrote:
> ....<snip>......
>> What about Steve Ciarcia's (sp?) SB180 single board computer as featured in
>> Byte Magazine (before it's demise). He had a column called "Circuit
>> Cellar", I think.
>
> Correct on all counts! The Ciarcia SBC was based on the Hitachi Z180.
> IMO, the Z180 is not a good example of a "z80 based" CPU. It broke the
> I/O opcodes that used the content of the C register to address ports.
> There was a good reason for that (too detailed to go into here), but
> unfortunately those opcodes were used in a lot of legacy Z80 applications.
> It was a nifty way to address multiple I/O ports just by changing the
> content of C. In order to run those old Z80 applications on a Z180, the
> parts of the code that used those opcodes had to be rewritten.
>
> The claim was that the Z180 was 100% binary code compatible with the Z80
> was obviously not true, and that might have been a factor in the lack of
> popularity of that CPU? It certainly never achieved the same level of
> acceptance as the venerable Z80! BTW, that same "glitch" might exist in
> the eZ80 as well. I just don't know.
>
> Roger

Ah, I had not known any of those details about the Z180.

I wonder if any of those got out into the real world and used much.

pH

>

[Bill McMullen]

"IMO, the Z180 is not a good example of a "z80 based" CPU. It broke the I/O opcodes that used the content of the C register to address ports."

Perhaps I'm just not experienced enough as I've only built more than a hundred Z80, Z180 and eZ80 systems, all of my own design and with totally self-written BIOS software as appropriate. With that being said, I don't understand the "broken" I/O instruction reference. In my experience, it's Z80 software that's broken when it is limited to hardware that doesn't implement the full Z80 capabilities.

I have heard people refer to the difference between 8-bit I/O and 16-bit I/O, but that argument always seems to devolve into the fact that someone wrote 8-bit I/O software for a Z80 system where the hardware designer chose not to implement the full 16-bit I/O capabilities. Indeed, the IN r,(C) and OUT (C),r instructions have exactly the same definitions in the Z80, Z180 and eZ80 User Manuals from Zilog. The primary difference in these 3 variants is that the Z180 reserves a block of 40h I/O address in the range 00x0h and the eZ80 reserves the entire 00xxh I/O address range for internal I/O addresses.

[[e-mail]]

On Friday, September 8, 2023 at 4:31:58 PM UTC-5, pH wrote:

> I wonder if any of those got out into the real world and used much.
>
> pH
>
I have one of those blank boards that I bought back in the day. I rediscovered it during a clearout last year but I wasn't able to find the EPROM code for download anywhere, so it sits in my PCB drawer unused. I'd love to get it up and running though.

[pH]

On 2023-09-19, ***@gmail.com <***@gmail.com> wrote:
> On Friday, September 8, 2023 at 4:31:58 PM UTC-5, pH wrote:
>
>> I wonder if any of those got out into the real world and used much.
>>
>> pH
>>
> I have one of those blank boards that I bought back in the day. I
rediscovered it during a clearout last year but I wasn't able to find
the EPROM code for download anywhere, so it sits in my PCB drawer unused. I
'd love to get it up and running though.


Maybe one of the hobby sites can write an eprom for you.
Here's a website that talks about it.

http://dunfield.classiccmp.org/mmint/

Maybe he'll pull his eprom and copy it for you.

pH

[[e-mail]]

On Tuesday, September 19, 2023 at 11:04:28 PM UTC-4, pH wrote:
> On 2023-09-19, ***@gmail.com <***@gmail.com> wrote:
> > On Friday, September 8, 2023 at 4:31:58 PM UTC-5, pH wrote:
> >
> > I have one of those blank boards that I bought back in the day. I
> rediscovered it during a clearout last year but I wasn't able to find
> the EPROM code for download anywhere, so it sits in my PCB drawer unused. I
> 'd love to get it up and running though.
> Maybe one of the hobby sites can write an eprom for you.
> Here's a website that talks about it.
>
> http://dunfield.classiccmp.org/mmint/
>
> Maybe he'll pull his eprom and copy it for you.
>
> pH

http://cini.classiccmp.org/systems.htm
Scroll down to "SB180/COMM180" and check out "Monitor source code (asm)":
http://cini.classiccmp.org/files/mon20.z80

[[e-mail]]

On Wednesday, September 20, 2023 at 1:22:27 AM UTC-5, ***@gmail.com wrote:
> On Tuesday, September 19, 2023 at 11:04:28 PM UTC-4, pH wrote:
> > On 2023-09-19, ***@gmail.com <***@gmail.com> wrote:
> > > On Friday, September 8, 2023 at 4:31:58 PM UTC-5, pH wrote:
> > >
> > > I have one of those blank boards that I bought back in the day. I
> > rediscovered it during a clearout last year but I wasn't able to find
> > the EPROM code for download anywhere, so it sits in my PCB drawer unused. I
> > 'd love to get it up and running though.
> > Maybe one of the hobby sites can write an eprom for you.
> > Here's a website that talks about it.
> >
> > http://dunfield.classiccmp.org/mmint/
> >
> > Maybe he'll pull his eprom and copy it for you.
> >
> > pH
> http://cini.classiccmp.org/systems.htm
> Scroll down to "SB180/COMM180" and check out "Monitor source code (asm)":
> http://cini.classiccmp.org/files/mon20.z80

Ah, excellent - thanks!

[dxforth]

On 9/09/2023 1:51 am, Roger Hanscom wrote:
> ...
> The claim was that the Z180 was 100% binary code compatible with the Z80 was obviously not true, and that might have been a factor in the lack of popularity of that CPU? It certainly never achieved the same level of acceptance as the venerable Z80! BTW, that same "glitch" might exist in the eZ80 as well. I just don't know.

eZ80 borrows 'unused' instructions (LD B,B LD C,C LD D,D LD E,E) saying if
the assembler encounters them they will be replaced with NOPs. So clearly
not 'binary compatible'. Has Zilog ever made such a claim? Here's what
they say in the eZ80 manual:

"The Z80 and Z180 programs are executed on an eZ80 CPU with little or no
modification."

[andrei-n]

On Tuesday, July 25, 2023 at 11:30:52 AM UTC+2, ladislau szilagyi wrote:
> Hi all,
>
> please describe, in your opinion, which should be the hardware characteristics of an "ideal" standalone Z80-based retro computer!
>
> By hardware characteristics, I mean: processor speed, RAM/EPROM size, storage media (type, storage capacity), keyboard interface, video screen interface, etc.
>
> thanks,
> Ladislau
Ideal for me would be if it doesn't use any chip more powerful than a Z80, and, of course only one Z80.
Even if it makes communication with outside more difficult. The keyboard should be mechanical, and look like a Kaypro II or ADM-3A.

[yeti]

andrei-n <***@gmail.com> writes:

> Ideal for me would be if it doesn't use any chip more powerful than a
> Z80, and, of course only one Z80.

I'd have no problems with other helpers like micro-controllers with some
big IFs attached:

IF and only IF the assembler for them exists on the OS of that Z80
system too and IF that Z80 system can program those helper chips.

Why?

To avoid the permanent need for a PC nanny to run strange SDKs of insane
sizes.

The ideal Z80 system should be an own complete "digitope".

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