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Thread: Measurement Systems DM6400 DRAM board info

  1. #1

    Default Measurement Systems DM6400 DRAM board info

    Hi

    My S100 box is equipped with a DM6400 DRAM card, the full on 64k monte. Only problems is, I think it's got some bad RAM. I used a ram check built into my Z80 ICE to detect that bits 4 and 7 are faulty around D500 but I don't know how the RAM is laid out on the board. I found a manual for it here but it appears to be missing the vital sections (schematic and board layout).

    Can anyone tell me which row of 4116s equates to which address range please (and which chip is the LSB)?

    Thanks
    JonB

  2. #2

    Default

    Never mind, it's working now...


    It lives, Masssster!.jpg

  3. #3
    Join Date
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    Default

    Excellent! DRAM's not too bad on a turnkey system, but if you end up running into lots of trouble with it, you might consider replacing with a SRAM board.

  4. #4

    Default

    Hi Glitch

    I spoke too soon. There was a very small click and the DRAM failed (or I am getting lots of errors on the memory). What a bother. What SRAM board do you suggest? I guess there is a modern one out there somewhere..?

  5. #5
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    There are modern ones from s100computers.com but IIRC those are mostly geared toward bigger systems (banked or 16-bit). There's a bunch of vintage RAM boards that work well, including those from CompuPro, Memory Merchant, Morrow, and a bunch that are actually the same board sold under different names (Coex, Digital Research, etc.)

  6. #6

    Default

    Those will be too expensive. S100 boards go for crazy money and usually in the US (so crazy shipping too).

    This is the main reason it has taken me so long to get an S100 machine in the first place.

  7. #7
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    I'll send you a PM, I've got a bunch of old stock boards and realize they're not actually solid gold

    Another option is to wire wrap or point-to-point solder one on a prototype board. Modern SRAMs make this pretty easy, but if you've never done S-100 bus interfacing before, it can be a bit challenging.

  8. #8
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    Don't forget that a 4116 is a triple rail beast (+5V, -5V and +12V) so my first port of call would be to measure all of the supply rails with respect to 0V/GND (especially if accompanied by a 'click' sound).

    Dave

  9. #9

    Default

    Excellent point Dave. Maybe the -5v regulator has given up..

  10. #10

    Default

    No, the voltages look good. Darn it.

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