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Thread: Memory upgrade for 286 motherboard.

  1. #1

    Default Memory upgrade for 286 motherboard.

    Hello. This is my first time posting here but I've been around for a while. I hope you can help me here!

    I have this generic 286 motherboard with an AMD 286 16 and chipset by "CHIPS", I wasn't able to find documentation for the jumper settings and such and I have exhausted my options. Here are some photos.

    https://photos.app.goo.gl/QeYCk1WjxjXiSCHW2

    https://photos.app.goo.gl/ULVuSChkeuQHBaft1

    Anyway... It works correctly, and as you can see it has 4 slots for SIPP memory and a bunch of DIP slots, which I don't what to put in as I couldn't find the documentation. I have 4x256kb SIPP sticks for 1MB and they work fine too, but I wanted to add more RAM to the system. So I bought this obscure Zenith board from eBay, thinking it was a RAM board (it hastn't arrived yet), but I think I bought the wrong card, as it has a 286 chip on it and what appear to be 2 BIOS chips. The card's reference is 052086 85-3261-01, and here's a picture.



    From what I could gather afterwards, this is a CPU + RAM board for a Zenith PC, in which the motherboard only consists of some ISA slots, and all the components are on expansion cards such as this. Do you think it will work on my generic 286 motherboard which already has a CPU, or if I remove the CPU and BIOS from the card?
    I saw another listing for a proper RAM board from the same seller, but it's also pulled from a Zenith PC, will it only work on a Zenith system or is ir like any other board? The card reference is 072286 85-3260-02A and here's a picture



    I've read that both cards can have from 256 to 640 KB of memory depending on the model. Worst case scenario I guess I could pull the memory chips and put them on my motherboard. In any case... Thanks for reading! ANy help will be appreciated!

  2. #2

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    Neither of those boards will work in your system, because they physically won't fit. Note how the connector is longer than a standard ISA slot.

  3. #3

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    Well... I feel very dumb now. Thanks for pointing that out! I guess all that's left now is harvesting the memory chips and hope for the best..

  4. #4

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    Yeah, those boards are for a system with a passive "backplane" board where the CPU and memory cards slot into it.

    You want something like an AST Rampage, or AST Sixpak, Intel aboveboard, or one of the many generic/clone memory expansion boards, though I would stick to name brand ones like AST or Intel just for ease of support, it may be hard or impossible to find jumper settings or software packs for some of the no-names.

    You could also just try larger SIPPs, its certainly possible the board could take larger than whats in there, wouldn't hurt anything to try 4x1mb even, and 1mb ones should be pretty inexpensive. NOTE: you can just buy 30pin SIMMs and solder pins to them, OR buy some 30pin SIMM sockets install the SIMMs into them and insert those into the SIPP socket.
    My Vintage computer/blog site
    Searching for a keyboard for a WYSEpc WY-1100.

  5. #5

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    Quote Originally Posted by RWallmow View Post
    Yeah, those boards are for a system with a passive "backplane" board where the CPU and memory cards slot into it.

    You want something like an AST Rampage, or AST Sixpak, Intel aboveboard, or one of the many generic/clone memory expansion boards, though I would stick to name brand ones like AST or Intel just for ease of support, it may be hard or impossible to find jumper settings or software packs for some of the no-names.

    You could also just try larger SIPPs, its certainly possible the board could take larger than whats in there, wouldn't hurt anything to try 4x1mb even, and 1mb ones should be pretty inexpensive. NOTE: you can just buy 30pin SIMMs and solder pins to them, OR buy some 30pin SIMM sockets install the SIMMs into them and insert those into the SIPP socket.
    Actually I bought those 30pin sockets some time ago, but couldn't use them because they were to large and the Sipp sockets where too close together and I completely forgot about them You just reminded me I had them. So I picked some riser pins and I stacked them together so the sockets would fit at different heights. And what do you know.. I sould fit 2 modules and the bios detects it! I have to get some more of those pins to fit the other two modules. If everything is detected I'll solder those pins on the sims! Thank you so much!

  6. #6

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    Well, I ended up soldering the pins.. but only 2MB are detected, no matter how I change places. I know all of thhem work because It also detects 2MB when I try sets of 2 sticks. Maybe thhe MB only supports 2MB? I also tried a bunch of BIOS ROMS I found online but all of them only see 512KB. Or maybe it can be set with jumpers? Also why would it have 4 SIPP sockets if the max is 2MB?
    I also read the chipset's datasheet, and it says it supports up to 8MB. Too bad I wasn't able to find jumper settings or any documentation on this particular board.

  7. #7

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    Is there an option in the BIOS to manually set the amount of memory? Maybe it's possible that it's just not auto-detecting correctly? Just a thought. Maybe it's limited and can't see more than 2mb on the SIPPs, and maybe it can take several MB in all those DIP/ZIP chip sockets. Maybe it's picky about the types of modules supported. Or maybe there's some jumper setting that's not well documented. Lots of variables here and unfortunately I am not familiar with that board or chipset.
    My Vintage computer/blog site
    Searching for a keyboard for a WYSEpc WY-1100.

  8. #8

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    What happens if you try 2 1MB and 2 256K SIPPs?

    FWIW, 2MB is probably enough for whatever you're going to do with a 286 anyway.
    If you're looking for DS/DD or DS/HD 3½" or 5¼" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

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  9. #9

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    This looks like a tough one to figure out. Problems:

    1. no documentation for jumper settings, which you probably need
    2. 6x6 DIP socket layout, so it's hard to know which sockets are in which banks (this is much more obvious when sockets are in a 4x9 layout)
    3. no idea whether SIPPs and DIPs can both be used at the same time (on some boards you could use one or the other but not both)

    It would probably help to get 36 1Mbit x 1 DIPs, and also 36 256Kbit x 1 DIPs (80ns if possible), put in all 36 of one kind and see what happens, then put in all 36 of the other kind and see what happens. Hopefully one set is recognized correctly but the other isn't. In that case you can start playing with jumpers to get the second set recognized (and thereby infer what those jumpers do).

    Some of those jumpers might be for wait states, if you end up getting slow memory (150ns or 200ns) the board may not work without correct wait states set, so try to get DIPs rated for as high a speed as you can.

    Then once that's done leave a set of DIPs in, add 4 SIPPs and start playing with the remaining jumpers to get an idea if any of them enable/disable SIPP versus DIP memory (or if you can have both).

    Kind of a slow process but I don't see much alternative except "plug in a lot of random stuff and live with whatever result you get".
    Last edited by kgober; December 4th, 2017 at 12:58 PM.

  10. #10

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    Sorry for the late update guys... My son was a little sick and I was pretty busy

    Anyway... I read on the cchipset's datasheet something about thhe memory modules having 9 chips. The modules I modded have 3 chips each, so (after testing all the BIOSes ROMs I could find on the internet), I decided to desolder the pins and resoldering on some 9 chips sims I had on my 386. Et voilį, the motherboard actually detected the 4MB, so that part's done.

    But, as this computer never let's you do anything that easily... I reran the benchmarks I ran with 2 MB, and something really weird happened. The results where actually worse with more RAM!!! I tried activating and desactivating EMS and XMS in every possible combination, I'm using EMM286.exe for expanded memory, and I always get the same results. About 10 to 15% drop in performance in all the tests. I also changed the wait states and other options regarding the memory in the BIOs with the same results. The test that caught my attention the most was the memory speed test. Where with 2MB I got 7400KB/s where with 4MB I got 7300KB/s.

    I guess after all the hassle, I will end up leaving the system with 2MB.

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