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

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

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

>>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...

....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

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.

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).

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

ladislau szilagyi <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 <ats@offog.org> <http://offog.org/>

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.

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...

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.

On 2023-07-25, Roger Hanscom <norwestrzh@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.

> 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

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 :)

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

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

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...

> 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.

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

> 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? :)

> 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…”. ;)

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

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

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