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Thread: ez80 S100 systems?

  1. #1
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    Default ez80 S100 systems?

    The title pretty much says it all--I'm a bit curious to find out if any Zilog EZ80 CPUs have been put on an S100 card. It would seem to be very appealing for multi-user and graphics applications of the basic Z80 architecture.

    I've got the EZ80 as an evaluation kit, as well as the Z180 and even the Rabbit R3000, but with the possible exception of the Z180, I don't recall seeing any of them on an S100 board.

    Of course, why anyone would want to put an R3000 on an S100 board eludes me...

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    I doubt it. I remember seeing a closed source CP/M 2.x port for ez80, but I believe it was for a standalone SBC. I put together an Arduino form factor board (ezDuino/80) a few years back, but ran out of steam porting RomWBW to it. It has USB COM1, 512K external SRAM, 5V tolerant I/O (buffers), SD card socket, and an I2C ADC. I even wrote a disassembler and emulator for the 24-bit extensions to test my code in a bubble before running it on the board as the Zilog tools were really sub-par compared to my normal counter-parts. I have a couple spare/assembled boards if someone has the time to take a real shot at it. Though you will need a ZDI programmer to flash it. I even started (but never finished) a ZDI programmer for Linux as the specs are all open standard.

    ez80 is a interesting MCU. Like most ISAs, you can intermix 16-bit and 24-bit instructions using a mode change or ad-hoc single instruction prefixes.

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    I recall my enthusiasm when I got the R3000 devkit (it was a long long time ago) and my subsequent disappointment when I realized that the Z80/8080 instruction set was incomplete (e.g. no DAA) enough that I wouldn't stand a chance of running CP/M or legacy applications without a lot of source-level mods. It went into a box and there it remains.

    But the ez80 is a different matter. It can run the usual Z80 code and is quite zippy. You'd think it'd be the perfect candidate for the S100 hobbyist.

    Of course, everything today is getting to be ARM.

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    Quote Originally Posted by eeguru View Post
    I doubt it. I remember seeing a closed source CP/M 2.x port for ez80, but I believe it was for a standalone SBC.
    There is a source-included port out there. The original site is gone, but there is a good mirror at:
    http://www.z80cpu.eu/mirrors/www.veg...CPM/index.html

    Chris Brock had a port of MP/M to the eZ80F91, but I haven't found any source or binaries out there, unlike the vegeneering version.


    I put together an Arduino form factor board (ezDuino/80) a few years back, but ran out of steam porting RomWBW to it. It has USB COM1, 512K external SRAM, 5V tolerant I/O (buffers), SD card socket, and an I2C ADC. I even wrote a disassembler and emulator for the 24-bit extensions to test my code in a bubble before running it on the board as the Zilog tools were really sub-par compared to my normal counter-parts. I have a couple spare/assembled boards if someone has the time to take a real shot at it. Though you will need a ZDI programmer to flash it. I even started (but never finished) a ZDI programmer for Linux as the specs are all open standard.
    Is any of this code available anywhere? I'd like to see the ZDI work especially. The TI calculator guys have some pretty good tools for the eZ80 now that the TI-84 Plus CE is running an eZ80 under the hood; the 'SPASM-NG' assembler handles the chip now. My porting is completely different, as I never really have been a CP/M guy, even though I've had Monteuma CP/M for the TRS-80 Model 4 for years. I'm going to try my hand at porting the TRS-80's LS-DOS 6 to several architectures; I'm on the hook for a guy to port it to a Lobo Max-80 (as well as to do TRS-80 Model II LS-DOS boot from hard drive), but to save wear and tear on the Max I'm going to play around with other platforms first, including a P112 and a RetroBrew SBC Z180 Mark IV along with an FPGA-based variant on the Papilio Duo platform. This will give me practice porting the more complex-than-CP/M LS-DOS LOWCORE to something non-TRS-80.

    ez80 is a interesting MCU. Like most ISAs, you can intermix 16-bit and 24-bit instructions using a mode change or ad-hoc single instruction prefixes.
    It is at that. The Zilog Z80-derived CPU's are more interesting, in my opinion, than the x86 CPUs. The Z380 in particular is a beast, and I've wanted a Z280 to play with for year (I have ten chips on order that should arrive soon, and I found the CPU280 (Tillman Reh) schematic, and I think popping the support circuits into the Papilio Duo may be just the ticket....).




    Quote Originally Posted by Chuck(G) View Post
    The title pretty much says it all--I'm a bit curious to find out if any Zilog EZ80 CPUs have been put on an S100 card. It would seem to be very appealing for multi-user and graphics applications of the basic Z80 architecture....
    Chuck, if there were an ECB-to-S100 'shim board' you could use the Z180 SBC Mark IV with ECB to drive the S-100. Or a shim board for the eZ80F91 ethernet modules; those would be cool. Or even a shim to let a P112 drive the S-100 bus. Perhaps an FPGA-based design, with the y80e core and an S-100 interface on a Papilio Duo or Pipistrello or similar?

    The biggest impediment to hobbyist S-100 boards may be the size of the board itself and the expense of getting one produced. The retrobrew (formerly known as N8VEM) guys do pretty much everything the S-100 bus can do on a smaller card with a more rugged bus interface connector. But the bus is similar enough the a shim could be done I would think. The single most expensive piece would likely be a gold-plated card edge.

    The eZ80 kits are still available from Digi-key and others; I bought a relatively inexpensive dev kit a couple of weeks ago from Digi-key myself. It's the 128k RAM version, but looks like a good one.

    I think the trick to interfacing one of these modules to S-100 is to use the eZ80F91's chip select outputs to drive /MREQ and /IOREQ of the Z80; this would allow the entire S-100 machine to essentially be a peripheral of the eZ80F91 (I'm thinking about doing the same thing with a TRS-80 Model 4P as the 'host' for the eZ80F91 module; an eZ80 version of the old H. I. Tech XLR8er). The hardest part is probably going to be figuring out how to interface a 50MHz CPU onto the much slower S-100; there is a 486 CPU for the S-100 out there that might show us how to go about that, though.

    This has been discussed a bit around here a few years ago: http://www.vcfed.org/forum/showthrea...-M-experiments

    EDIT: The ez80p archive is still on Sourceforge and accessible with subversion:
    https://sourceforge.net/p/ez80p/code/HEAD/tree/
    Last edited by lowen; October 17th, 2016 at 04:59 AM. Reason: Added reply to Chuck and a link to a previsou VCF thread
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    I have an eZ80F91 dev kit somewhere. I never got around to do anything with it, but the idea was to run CP/M on it, in some variant. Well, I'm more interested in the process of getting it to work, not just run CP/M.

  6. #6

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    Quote Originally Posted by lowen View Post
    The biggest impediment to hobbyist S-100 boards may be the size of the board itself and the expense of getting one produced. The retrobrew (formerly known as N8VEM) guys do pretty much everything the S-100 bus can do on a smaller card with a more rugged bus interface connector. But the bus is similar enough the a shim could be done I would think. The single most expensive piece would likely be a gold-plated card edge.
    It doesn't have to be gold, surely? I've seen plenty of ISA cards with tin fingers, and while it looks cheap as hell it certainly doesn't stop them from working.
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    I was mildly surprised at the absence of one, given the capabilities of the ez80 CPU. I'dve thought that the S100 community would have jumped on this one.

    Of course, you don't need an S100 box to use this--in fact, the S100 PCB size would seem to be almost ludicrous. One could assemble a system with all the capabilities imaginable in a board the size of a package of cigarettes. So maybe that's the real issue.

  8. #8
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    The biggest impediment to hobbyist S-100 boards may be the size of the board itself and the expense of getting one produced. The retrobrew (formerly known as N8VEM) guys do pretty much everything the S-100 bus can do on a smaller card with a more rugged bus interface connector. But the bus is similar enough the a shim could be done I would think. The single most expensive piece would likely be a gold-plated card edge.
    Quote Originally Posted by commodorejohn View Post
    It doesn't have to be gold, surely? I've seen plenty of ISA cards with tin fingers, and while it looks cheap as hell it certainly doesn't stop them from working.
    John Monahan at S100Computers.com has created over a dozen new-design hobby S-100 boards and routinely sells them in board runs for ~$20/board. Two or three other members have also done boards lately (JAIR-8080, FPMini, MEMPlus, etc)

    You just need a decent batch size and the costs are perfectly reasonable.

    KiCad layout software is free.

    I've thought that a Z180 or eZ80 CPU board would be a nice addition to the other S100Computers boards, which now top out at a 486. Grab a copy of KiCAD, download the KiCAD files for the excellt Z80 V2 board from John's site, and get cracking.

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    It's been my thought that an ez80 board might actually be easier (in terms of components) to source, if one admits SMT as a possibility. 16MB of memory is nothing now, but would have been almost unthinkable in 1985. Of course, with CPU, a few peripherals and memory all on the same board, you'd have to implement only a portion of the available addressing space on the S100 bus.

  10. #10

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    Quote Originally Posted by lowen View Post
    There is a source-included port out there. The original site is gone, but there is a good mirror at:
    http://www.z80cpu.eu/mirrors/www.veg...CPM/index.html
    I built the Vegeneering eZ80 CP/M machine many years ago (really, it's the dev board with an SD card wired to it. It worked well, I've always wondered why the eZ80 was never picked up as the Ultimate CP/M platform, really. Like you say, it'd fit in a tiny box but be very powerful. Hmm. That sounds like another project on the stack...

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