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Thread: Board that (reportedly) can handle 64mb RAM only sees 16mb?

  1. #1
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    Default Board that (reportedly) can handle 64mb RAM only sees 16mb?

    So, I have a DX2-66 plugged into this board here. Specs say it'll handle 64mb, and I have a pair of 32mb EDO sticks I know work, but this system won't see them at all. I plug one stick into any of the four banks, won't boot. I plug two sticks in, still won't boot. Okay fine, for some reason it doesnt like 32mb sticks, moving on.

    Beyond the 32mb sticks, I have a bunch of 4mb and one 8mb. Board sees the 8mb stick fine. I plug two 4mb sticks in with it and it gets up to 16mb fine. I plug a 3rd 4mb stick in... stays at 16mb. Should be 20mb, but the system only reports 16. I can plug four 4mb sticks in and get 16mb just fine, so theres no issues with any of the banks.

    Anyone have any ideas on what could be causing this? Near as I can tell there are no jumpers or BIOS settings that affect RAM limits, and it seems odd that some sort of defect or fault with the board would cause this. The board does handle faster 486s and Pentium Overdrives, is it possible it only handles that much RAM with the faster processors?

  2. #2

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    Go back and look at the dram configuration chart you posted. You have been trying some invalid configurations.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  3. #3
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    Many 486 chipsets didn't have memory controllers that properly support EDO memory, and will only support specific memory capacities using FPM modules only.

    I have an AST Advantage 486 SX 25 which has a maximum memory capacity of 64 MB, but only if FPM modules are used. It only supports 32 MB using EDO modules.

    Mixing and matching EDO and FPM sticks can also cause weird problems.

  4. #4

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    I have a 486 board with similar issues. It has four 30-pin slots and two 72-pin ones. I can put 32MB in it in almost any configuration of 30- and 72-pin modules and it appears to be recognised by the BIOS. Will even pass various RAM checks. But actually trying to use it (e.g. make a 16MB RAM drive so the next 16MB is in use) crashes any application that accesses it. I've tried with clean boot + HIMEM.SYS but the result is always the same.

    Not a big deal as 16MB is fine for a DOS 486 in most cases, but it took me a while to work out where all the random hangs were coming from. Unfortunately, unlike you I don't even have a motherboard manual for this one.

    There are certainly some quirky 486 boards out there.

  5. #5
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    Quote Originally Posted by GiGaBiTe View Post
    Many 486 chipsets didn't have memory controllers that properly support EDO memory, and will only support specific memory capacities using FPM modules only.
    I've never found a satisfying answer as to whether or not EDO memory had a benefit; any thoughts? I remember it being highly touted when I purchased a P120 that used EDO in the 1990s, but was there any actual advantage to EDO vs. non-EDO RAM? I never felt a massive speed boost over that of a P90 I used at work at the time (somewhat unrelated, I put an ATI 3D card in the P120 and was quite underwhelmed by the "accelerated" programs it came with; neither were particularly happy purchases).
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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    Quote Originally Posted by Trixter View Post
    I've never found a satisfying answer as to whether or not EDO memory had a benefit; any thoughts? I remember it being highly touted when I purchased a P120 that used EDO in the 1990s, but was there any actual advantage to EDO vs. non-EDO RAM? I never felt a massive speed boost over that of a P90 I used at work at the time (somewhat unrelated, I put an ATI 3D card in the P120 and was quite underwhelmed by the "accelerated" programs it came with; neither were particularly happy purchases).
    EDO did have a benefit, but it was quite marginal.
    EDO stands for Extended Data Out, which meant that you could overlap data transfer with addressing to a limited extent, allowing basic 'pipelined' access, shaving off a few cycles (5% faster than fast-page memory was quoted).
    Perhaps it was less spectacular because Pentiums already came with reasonably large L1 and L2 caches, which would mask the difference.

  7. #7
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    Quote Originally Posted by Trixter View Post
    I've never found a satisfying answer as to whether or not EDO memory had a benefit; any thoughts? I remember it being highly touted when I purchased a P120 that used EDO in the 1990s, but was there any actual advantage to EDO vs. non-EDO RAM? I never felt a massive speed boost over that of a P90 I used at work at the time (somewhat unrelated, I put an ATI 3D card in the P120 and was quite underwhelmed by the "accelerated" programs it came with; neither were particularly happy purchases).
    EDO had a slight benefit in applications that depended on memory bandwidth, but otherwise had little impact other than on the wallet. I guess another application that EDO was better at is the very few systems that used onboard memory as video memory gained a bit of performance.

    As for the ATI Rage card, the whole series was junk. The drivers were poor, no proper OpenGL support and they never offloaded enough of the 3D workload (like Voodoo2/3 or Nvidia TNT) to make a difference.

  8. #8
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    Quote Originally Posted by GiGaBiTe View Post
    As for the ATI Rage card, the whole series was junk. The drivers were poor, no proper OpenGL support and they never offloaded enough of the 3D workload (like Voodoo2/3 or Nvidia TNT) to make a difference.
    I concur. I started up the accelerated version of Wipeout that came with the card and it ran in 320x200 16-bit-color at the same framerate as the software-only 8-bit-color version. I actually thought something was wrong and called ATI to see if my card needed replacement. I thought "accelerated" meant faster, not "nicer-looking at the same speed".
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  9. #9
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    I think very late Rage series cards (like the Rage 128, 128 Pro and Fury) had a basic triangle setup engine, but still could never really compete with other competitor offerings at the time.

    OEMs loved them though because they were dirt cheap. I think pretty much every OEM used some Rage chip during that time.

  10. #10

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    Most 486 chipsets did not have any special support for EDO. There is an old Micron article on EDO compatibility with FPM DRAMs:
    http://web.archive.org/web/200308172...notes/DT40.pdf
    Last edited by yuhong; March 26th, 2017 at 09:20 AM.

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