PDA

View Full Version : CPU280 discussion and information thread.



lowen
December 15th, 2016, 08:09 AM
Over 20 years ago a gifted engineer, Tilmann Reh, designed what some have considered the ultimate CP/M single-board computer, the CPU280. Now, that is a very subjective statement; some might say that the P112 with a CPU upgrade to 24.5MHz would be the 'Ultimate' and it's not the focus of this thread to argue about 'which is the ultimate.' Although David Brooks' P112 should be a reference design as well; you can learn a lot about designing stable crystal oscillator sections of a PCB from the P112 design! The focus of this thread is on a budding CPU280 revival, much like David Griffith's bringing back of the P112.

The CPU280 is based on the Zilog Z280 CPU at 12.288 MHz with up to 4MB of RAM on board, on-board floppy controller, two serial ports, boot-from-EPROM (a pair of them), and I/O through the common ECB bus. The Z280 is run in the 16-bit Z-BUS (Z8000-bus-and-peripheral-compatible) mode; thus an EVEN and an ODD EPROM.

Tilmann wrote in a comp.os.cpm post that only about 50 were ever built during the original run. The project was dropped once Zilog announced that production of the Z280 was stopping in early 1996. As early as TCJ issue #77 (available freely online), Tilmann had declared the board obsolete due to the difficulty of finding the parts, especially the Z280 CPU.

A few months ago, I became interested in the 'retrobrew' scene (the group formerly known as the 'N8VEM group') and begin investigating some of these SBC's, with an eye to porting the TRS-80 line's LS-DOS to what is ordinarily a CP/M-only board. (I'm porting LS-DOS 6 to the Lobo MAX-80, and to save wear-and-tear on the MAX-80 I'm learning the ropes of porting LS-DOS on newer hardware first).

I ordered two P112 kits from David Griffith and have built but not yet tested one of them. I've ordered a couple of bare boards for the retrobrew SBC-180 MkIV, and have even ordered an eZ80F91 development board from Mouser to play with. CP/M or a derivative such as ZSDOS is the native OS for these boards, of course, and the ideal OS for testing them prior to porting something else to them. There are other OSes, too, such as UZI-180, UZI-280, and Fuzix to play with.

I have corresponded with Tilmann over the last couple of weeks, and I have just ordered ten bare CPU280 boards from a PCB vendor. The Z280 CPU is more plentiful now than it had been (I have purchased 20 of them in the last four months), and the other chips are available if you look for a little while. So I am going to build up at least one CPU280 and will have a few bare boards left, I'm sure.

Tilmann has given me permission to share the English translations of the German manuals. Let me say that these are very well-written and describe the design in great detail. I've shared with the retrobrewcomputers.org group, since the CPU280 is both vintage and retrobrew (the design and first board run were in 1990, 26 years ago), and I encourage you to go there to obtain them (the zip file is too large for this forum's restrictions or I would upload here).

I'll let the forum know how the construction goes.....

If anyone here has or had a CPU280, I'd like to hear your story.

lowen
December 27th, 2016, 11:32 AM
And a few pics are in order...... Here is a built CPU280 I just received:
3503635037

I have in-hand ten bare boards, now, and am getting ready to build the first one. Once I have a successful build documented, I'll open up for orders on bare boards and/or parts (probably just the hard-to-find parts and a link to a Mouser project that I'm working up). I have been able to find all of the IC's, so it is possible.

One of the strong points of the CPU280 is the format interchangability with many CP/M variants; the ability to control 3.5, 5.25, and 8 inch drives natively, and a CP/M 3 based OS.

I'll update the thread as needed; I might even blogify it.....

KC9UDX
December 27th, 2016, 12:16 PM
Cover those windows! :)

ZIP chips? Yuck!

archeocomp
December 27th, 2016, 12:46 PM
That Dallas real time clock calendar is a bad idea. In 10 years its battery will be dead.

KC9UDX
December 27th, 2016, 01:20 PM
That Dallas real time clock calendar is a bad idea. In 10 years its battery will be dead.

I sure hope so. I would expect that of a 35 year old battery.

It may already be dead.

lowen
December 27th, 2016, 02:00 PM
The ZIP DRAM chips are readily available. How else can you get 2Mx16 bit RAM (4MB) on a single eurocard? But with 1Mx4 bit nibble fast-page-mode RAM a good density, for 1990 vintage, is doable.

The uncovered windows are a different sort of problem, but I have all the source software so even if the EPROMS are toast I have the code, and some SST27SF512 replacements in hand... as well as two new (from Mouser) DS12887A units. I fully expect the DS1287's battery to be long dead, but that's ok. This unit is one of only 50 or so CPU280's ever made, and so I'm not complaining.

KC9UDX
December 27th, 2016, 02:19 PM
It's a good thing they're readily available. Every time I need to install 32 of them, I wreck 48 of em.

lowen
December 29th, 2016, 09:55 AM
It's a good thing they're readily available. Every time I need to install 32 of them, I wreck 48 of em.

:-) You'd just love a board I have here, then, that has hundreds of ZIP-packaged VRAM modules...... (framebuffer from an old SGI Personal IRIS).....

I've successfully read both EPROMs, and I haven't seen any evidence of corruption. The SRecord package ( http://srecord.sourceforge.net/ ) is a marvelous thing to help work with EPROM dumps.....

I'll still probably build from the assembler sources, though, as I'm not using 27C256's in my builds. The SST27SF512 parts (no longer manufactured, but relatively common in the automotive ECM modding scene) will be what I use in for my own builds. Making sure you get a real SST27SF512 (a 27C512 pin-compatible flash chip) and no a remarked one-time-programmable 27C512 is the catch, here, and I bought the five 27SF512's I have from a reputable dealer who guarantees that they're not counterfeit. (I need to test them; write one pattern to the chip, read and check, erase and write a different pattern, read and check). Apparently the market is very full of counterfeits, OTP ROMs being remarked and passed off as the flash chip. (datasheet for SST27SF512: http://www.futurlec.com/Memory/SST27SF512.shtml ).

KC9UDX
December 29th, 2016, 02:19 PM
I've got an A2386. I think it has 32 ZIPs. I'm pretty sure I robbed most of them populating A3000s, though.

lowen
December 30th, 2016, 05:15 AM
ZIPs are definitely suboptimal when socketed; they were really meant to be soldered in. The pinout makes good layout, especially of the power and ground, a bit easier than DIPs. Tilmann used ZIPs for their size, since he was running out of room on the CPU280's eurocard but wanted to maximize the amount of RAM. The Amiga designers probably had the same thought.

It seemed like a good idea at the time.

fritzeflink
January 3rd, 2017, 05:38 AM
One of the strong points of the CPU280 is the format interchangability with many CP/M variants; the ability to control 3.5, 5.25, and 8 inch drives natively, and a CP/M 3 based OS.


Just for information as I give my T.Reh CPU280 system away years ago.

http://oldcomputers.dyndns.org/public/pub/rechner/zilog/z280/

You'll find the manuals for Zilog Z280 here:
http://oldcomputers.dyndns.org/public/pub/rechner/zilog/z280/manual/

Other once in the net have missing pages and are not completed.

lowen
January 16th, 2017, 05:15 AM
Fritzeflink, thanks for the links.

Update: Of the 10 bare 'beta' boards I had fabricated, 6 are already spoken for with two already in the hands of a beta tester/builder. I have several interested in a production run board and/or a kit.

The one original CPU280 that I received from Tilmann Reh is now successfully booting from EPROM. Wayne W. on the RetrobrewComputers.org forums gave me a serious tip and pointed me to the 'zxcc' CP/M emulator, which can run CP/M programs from a Linux (or Windows; download the zip in the thread on the retrobrewcomputers.org forum) command line, so building the software is a snap (literally: the build on my Dell Precision M6700 quad-core i7 takes 0.925 seconds), now, and I burned the EPROM binaries from Linux on my TL866A.

Progress, one step at a time.

fritzeflink
January 16th, 2017, 05:48 AM
Fritzeflink, thanks for the links.

Update: Of the 10 bare 'beta' boards I had fabricated, 6 are already spoken for with two already in the hands of a beta tester/builder. I have several interested in a production run board and/or a kit.

The one original CPU280 that I received from Tilmann Reh is now successfully booting from EPROM. Wayne W. on the RetrobrewComputers.org forums gave me a serious tip and pointed me to the 'zxcc' CP/M emulator, which can run CP/M programs from a Linux (or Windows; download the zip in the thread on the retrobrewcomputers.org forum) command line, so building the software is a snap (literally: the build on my Dell Precision M6700 quad-core i7 takes 0.925 seconds), now, and I burned the EPROM binaries from Linux on my TL866A.

Progress, one step at a time.

Nice info that the Reh 280 ist running. My old system now is in the hands of Andreas Gerlich - founder of YAZE AG. As time goes by today I'll never give such a wonderful system away but years ago I had a live change and for those it was the best way to cut old pigtails. If today someone will say " here you can get my Reh280 for free" I'll take it as fast as I can. But that's not the possibility so I collect my old EACA Video Genie computers I began with.

For interesting - are there some more information about you Z280 SBC ?

lowen
January 16th, 2017, 06:10 AM
...
For interesting - are there some more information about you Z280 SBC ?

Yeah; https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=93&start=0& is the thread on the retrobrewcomputers.org site.

In a nutshell, I got gerbers from Tilmann and have had ten new bare CPU280 boards fabricated from his gerbers. All of the chips are relatively easy to find from parts recyclers like UTsource, including the Z280 CPU. I have a few beta testers lined up, with one already building the first new CPU280 in at least fifteen years. So it's basically a revival of Tilmann's CPU280.

I am talking with several via email on a new Z280 SBC design that uses some more modern things and removes the floppy controller; using SIMMs for one and SD card storage for another and a single 8-bit Flash ROM instead of two relatively difficult to work with EPROMs. That kind of thing.

lowen
January 30th, 2017, 05:51 AM
Update for January 30:

One of the beta board builders has a successful boot from EPROM. So the board fabrication looks to have been successful, and I'm getting ready within the next couple of weeks to place the order for another run. I haven't decided yet how many to get this time; it will depend upon the amount of interest.

I will encourage anyone who is interested in a board to pop on in to the thread on the retrobrewcomputers.org forum, as that is the primary coordination location.

Tasks left to do include building floppy images with the utilities necessary to really use the board, and some documentation on the build process for the hardware and the software. I'm also going to be ordering a short run of a few of the REH-ECB-IDE boards, eventually. I need to put mine in a case and get a backplane built first.

lowen
June 1st, 2017, 07:08 AM
June 1 update:

Several CPU280s have been successfully built and are running. I had a second run of ten boards made, and have sent out two of those, with three more to send out Monday and one put on hold. Wayne W put together a github for the CPU280 code at https://github.com/wwarthen/CPU280 and has ready-to-use EPROM and floppy disk images available as well as the source code, with Tilmann Reh's permission and blessing.

If you're interested in building one of these, please let me know by PM. This is not an ideal 'first kit' to build due to the very tight layout and some special techniques that need to be used during construction. (If you want an ideal 'first kit' to build the RC2014 Z80 machine would be one; an ideal 'second kit' would be the P112; the CPU280 is significantly more difficult to get up and running than the P112.)

zenxyzzy
August 8th, 2017, 12:38 PM
June 1 update:

Several CPU280s have been successfully built and are running. I had a second run of ten boards made, and have sent out two of those, with three more to send out Monday and one put on hold. Wayne W put together a github for the CPU280 code at https://github.com/wwarthen/CPU280 and has ready-to-use EPROM and floppy disk images available as well as the source code, with Tilmann Reh's permission and blessing.

If you're interested in building one of these, please let me know by PM. This is not an ideal 'first kit' to build due to the very tight layout and some special techniques that need to be used during construction. (If you want an ideal 'first kit' to build the RC2014 Z80 machine would be one; an ideal 'second kit' would be the P112; the CPU280 is significantly more difficult to get up and running than the P112.)
I've got a few Z280's from back in the day (i got a free sample from zilog!)
and also picked a few up on ebay (i know, risky.. i got a lot of duff z80-20's that would
only do 6 mhz). but my z280's look ok, obviously pulls.

anyhow, issue #2 of supermicro, which I am still looking for, is said to have an S100 z280
board with schematics. until I can fab one of those up, I'm interested in joining your
merry band.

I want to run unix v7 on it; specifically, bsd 2.11, since the z280 has all the muscle of a pdp-11.
I can port this fairly easily, as I am a unix kernel hacker from the bad old days.

got any left? take money from me!

--curt

zenxyzzy
November 1st, 2017, 12:36 PM
yay! finally got the reh280 card fully built (sourcing parts via china is a PITA - everything counterfeit)
so, I plugged it in to my 8 slot ecb mobo, and 2 tantalum caps promptly explode. (both the input filters).
I mis-read the polarity markings. no board damage, but I get to desolder and double check everything to make
sure no traces got fried.

--curt