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Thread: Multibus open hardware?

  1. #1
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    Default Multibus open hardware?

    Is there such a thing? Would enough people be interested in it to warrant it? There doesn't seem to be any open hardware Multibus projects AFAIK.

    The situation seems ripe for a Multibus open hardware project but I don't want to push something no one else or very few are interested in pursuing.

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    We still run MULTIBUS 1 equipment at work.

    In fact, I am re-manufacturing some of it as we speak (a 4-port intelligent synchronous/asynchronous communications card to be exact)...

    What are you thinking of?

    I would be interested in potentially two things at this point in time. Either:

    A MULTIBUS 1 interface to some other (= more modern) bus architecture (e.g. PCI or VMEx64) or

    An FPGA-based MULTIBUS 1 card. A 'decent' FPGA - one with some large BRAM, embedded PowerPC processor to run Linux and a fiber or ETHERNET port with a couple of RS232 serial ports.

    Is that what you are thinking - or am I reading more into your post than you were thinking of?

    Dave

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    Hi

    I was thinking more along the lines of a hobbyist open hardware approach somewhat similar to what we did on S-100 or ECB.

    Right now (AFAIK) there are no open hardware Multibus designs or the infrastructure to support it so any project involves Multibus basically means starting completely from scratch. For instance, board outlines, part libraries for P1 and P2, example schematics in KiCAD (open source) format, etc. All those things you would need to even start a project. Also there doesn't seem to be any much, if any, hobbyists building their own Multibus boards so there are skills and knowledge would need to be built up as well. Without a Multibus template each project has to carry all the burden and I think that suppresses a lot of people from even starting or considering their own.

    I think your ideas are great for Multibus projects but I think they are more graduate level where I was thinking more like freshman introductory level projects to "prime the pump" and get things rolling. [I asked a similar question on the S-100 Google Group so I'll weave in part of my thread from there since it is similar]

    What I am suggesting is more of a "crawl, walk, run" approach. IMO, there are really three basic kinds of boards for any parallel bus in rising order of complexity: IO, memory, and processor.

    In order to get started with a something well documented and low risk technically but important from an infrastructure perspective. Like the simple IO board from Application Note AP-28A which is really just a pair of 8255 PPIs. Develop that board which would provide the board outline, connectors, and general schematic building blocks for later more sophisticated IO boards like IDE, serial, etc. Or maybe start with an even lower threshold like a prototyping board.

    Once IO boards are working and reliable build static RAM and Flash ROM memory boards. Again, keep it simple as possible building on the lessons from the IO boards and build up that open hardware Multibus infrastructure.

    Finally build processor boards starting with 8085, move up to 8088, 8086, etc. Once those are working then attempt the non-Intel processors or more aggressive designs like bus bridges, FPGAs, etc. People are doing stuff like that on S-100 now but only after many years of slow progress going up the ladder of complexity.

    Obviously this is a big long term project but the model has worked at least twice in the past. Once with the ECB board collection and again with the S-100 boards. It is too big for a single individual and would require significant investment in time, effort, and money.

    I would be happy to design a simple open hardware Multibus board and put the design out there but I am doing some "market research" first before I spend time on it. Multibus is different than S-100 and ECB in that those busses are dominated by hobbyists while Multibus systems are still in use in industry and in some cases commercially available.

    There are things I'd be happy to do like build a KiCAD version of an IO board but not chase down other people to build it, buy boards, distribute boards, etc. In other words, for this to work there has to be some level sponsorship and group participation or it is just me pushing an idea no one else really wants.

    I don't know what the level of interest is out there or what people's capabilities are. Maybe jumping to a PowerPC processor board is feasible as a first step but it seems overly ambitious to me and is way beyond my skill level.

    Thanks, Andrew Lynch
    Last edited by lynchaj; May 19th, 2017 at 08:20 AM.

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    Quote Originally Posted by daver2 View Post
    Is that what you are thinking - or am I reading more into your post than you were thinking of?

    Dave
    Hi Dave, since you are still running Multibus at work can you answer a few questions for me?

    What a people running Multibus doing for mass storage? Are IDE/CF/SATA controllers available for Multibus? If not are people still running their original ST506/412 controllers with legacy MFM type hard disks? Floppy drives? What about networking?

    The Multibus controllers I saw in industry were booting from solid state ROM boards to load their controller code. No spinning media due to the environment. The boards probably cost a mid-size fortune back in the day though.

    I think simple hobbyist level boards are certainly achievable. For instance, parallel interface, IDE/CF interface, serial interface, prototyping board, simple backplane, simple PS/2 keyboard & mouse, possibly simple FDC, possibly simple 8-bit Ethernet, even possibly simple 8-bit VGA. Simple SRAM and Flash ROM boards too.

    Projects can be kept simple to increase their likelihood of success. Runaway complexity kills these projects. Thanks, Andrew Lynch

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    Andrew, have you seen 1995 brochure. Several CPU boards had both SCSI and IDE integrated on them.

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    Hi, No. Thanks for the brochure. Interesting stuff.

    OK, say you have a legacy Multibus I embedded controller. It's been running for many years and the hard drive is slowly failing. SCSI, IDE, ST506/412 or whatever. Can you get a replacement IDE controller and keep going or do you need a replacement CPU with drive controller? Its not a LMGTFY as I've already tried.

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    You can probably find a Multibus SCSI controller, but IDE is so little silicon to interface, that it's doubtful that you could find it alone on a card. Perhaps as a daughterboard...

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    Andrew,

    All of our Multibus nodes are diskless. They boot over a network from a host machine (non MULTIBUS). A small EPROM (located on the CPU card of each Multibus node) contains the Intel iSDM 286 debug monitor and our bespoke boot code via our communications cards.

    Incidentally, I have the Intel relocatable object code for the 286 debug monitor. No sources, but all the 'device specific' configuration for the debug monitor is done outside of the relocatable object code. I also have the relevant tools (PLM, assembler, linker etc.) running on DOS. I also have cross development tools that run under RSX-11M; so when I have built my J11 S100 card...

    The intelligent communications card I am finishing off contains an 8086 CPU, two dual UARTS, local EPROM and SRAM (only small amounts), two Intel counter timer chips. Mainly used as baud rate generators for the UARTS - but one is used as a real time clock interrupt for the CPU. The card can become a bus master (to transfer data packets to/from MULTIBUS memory) and as a bus slave to receive configuration commands etc. From another bus master (a dedicated control CPU).

    I have been involved with MULTIBUS 1 equipment since the early 80's - so more than willing to help out where I can here.

    Regards,

    Dave
    Last edited by daver2; May 20th, 2017 at 12:02 AM.

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    Is your communications controller proprietary or open hardware? Is it Multibus I?

    The Multibus controllers I've seen have been mostly diskless due to the environment. Occasionally there are disks but usually indoors in a lab setting.

    It seems the diskless systems can run practically forever.

    I'd like to start a hobbyist Multibus project with simple, single function Multibus boards. Sort of like when John and I did with the S-100 boards. However, I got really frustrated when the boards just kept getting more and more complicated and almost indecipherable. There is goodness in keeping things simple.

  10. #10

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    Thinks like standard bus arbitrators in fpga or such
    would be of value as well as board layouts.
    Dwight

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