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Thread: Cache for Zenith 386SX16

  1. #1
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    Default Cache for Zenith 386SX16

    I'm looking for a cache simm for a Zenith 386SX16 circa 1988. According to the manual they came in 4k (what I have) 16K, 32K, 64 K and 128 K flavors. This is the small desktop machine that Zenith made, not the AT sized machine. I'm not sure whether they are vaporware or not.

  2. #2
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    Default

    Could you post a photo of the front and back of your 4K cache? I think the probability of finding a Zenith-branded cache SIMM is pretty low, but maybe a generic model would work.

  3. #3
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    Default

    What is the model number of the computer? By any chance is this a model Z-5100? I have a Zenith Z-386/25 (the big AT machine) that has a separate cache card but it is proprietary Zenith. If your cache card is proprietary like mine, your options are really limited.
    You may try contacting someone at :

    www.zdsparts.com

    They may have the part you are looking for even if it isn't listed on their website.

  4. #4
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    Default cache card

    I'm about 99% certain that the card is proprietary since the only machines I've ever seen them in are Zenith. It is a 72 pin card, that oddly enough a 72 pin SIMM will physically fit.

    The model Number is ZMV-3726-EK.

    I contacted the people at ZDSPARTS about 10 years ago, and they didn't have any modules then. I doubt that time has increased their (lack of) supply.

    Besides I bought the machine at a company computer sale in 1993 for the whopping sum of $20, intending to throw the machine away and use the nice flatscreen ZCM-1492 color CRT on my smoking fast 486-DX4 120 machine. I couldn't justify paying what they would want for such an item.

    Somewhere along the way the Zenith became my hobby machine and the monitor died an ignominious death from a fly-back transformer failure.
    Attached Images Attached Images
    Last edited by dpatten; January 11th, 2009 at 06:06 AM. Reason: no attachment

  5. #5
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    Default

    There are standard JEDEC SIMM pinouts for cache SRAM, believe it or not. But I've never seen a 16-bit wide one in a 72 pin SIMM. For a 4K unit, this looks incredibly complex.

    Well, maybe this will look familiar to someone.

  6. #6
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    Default I misspoke

    According to the manual for this machine which I have just dug out, the available cache RAM SIMMs for this model were:

    4k, organized as 2k x 16, direct map, 3 tag. (Which I have.)

    8k, organized as 4k x 16, direct map, 3 tag.

    32K, organized as 16k x 16, direct map, 2 tag.

    128K, organized as 64K x 16, direct map, 1 tag

    (128K cache memory upgrade available Model ZA-3900-CU)

    I was considering hacking away at one of the 4K cache modules I have and trying to add higher density chips, but it looks like that would only net me 8k.

    Anybody?

  7. #7
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    Default Pal

    Chuck(G) said...this looks incredibly complex.
    That's Zenith for you. The same straightforward engineering they put into their television chassis.

    I think that PAL in the middle might make your life miserable if you try to hack it higher.
    By manual you mean user guide, or tech ref. ?
    The chips need 11 address lines, so it would be amusing to figure out if the rest of them (from the socket) are wired on the board, or if each board ( 4 , 8 , etc ) was unique. Do you have a shot of the back as well ?

    patscc
    Last edited by patscc; January 13th, 2009 at 05:12 PM. Reason: grammer

  8. #8
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    Default

    There is nothing on the back side. unless you want to look at the solder joints. The card is hybrid SMT/thruhole. All of the DIPs are thru hole.

    The manual I have is, alas, only a user's manual, nothing with schematics. I sadly am neither technically inclined enough to map out the circuit or motivationally inclined to do so.

  9. #9

    Default

    Hi there,

    I have a 72pin 4kb 16bit cache SIMM module amongst my massive collection. There's nothing about Zenith on there, and the only sticker that was on it is gone, but the markings on there are:
    4KB16B3T / 05-3540-01 / 3540V4

    I do have XT/286/386/486/586/P2/P3/P4 motherboards, but it doesn't fit in any of them.

  10. #10
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    Default

    That's the exact same cache simm that I have on my motherboard that I also have 2 spares of. I'm looking for the higher capacity 128k or 32k version.

    At least you now know that your chip fits a Zenith 386SX16.

    The parts I am looking for would probably have a number something like :

    32KB16B2T or 128KB16B1T
    Last edited by dpatten; January 26th, 2009 at 09:51 AM. Reason: add part #s

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