Many VLB boards do not have a Flash BIOS, rather, you purchase and program another BIOS chip using a hardware programmer and then swap it.

Curious why you want to try and run 128Mb ram on a 486 board, max for true ms DOS is 64Mb iirc.

jakethompson1 wrote on 2025-04-26, 00:26:

Many VLB boards do not have a Flash BIOS, rather, you purchase and program another BIOS chip using a hardware programmer and then swap it.

Thank you for that information.

Horun wrote on 2025-04-26, 00:35:

Curious why you want to try and run 128Mb ram on a 486 board, max for true ms DOS is 64Mb iirc.

Just wanted to max it out to see how far I can push it. I've installed Windows 2000 successfully with 64MB RAM.

ddoyle525 wrote on 2025-04-26, 06:35:

Horun wrote on 2025-04-26, 00:35:

Curious why you want to try and run 128Mb ram on a 486 board, max for true ms DOS is 64Mb iirc.

Just wanted to max it out to see how far I can push it. I've installed Windows 2000 successfully with 64MB RAM.

It might actually be slower with 128MB of RAM if the maximum cacheable range the chipset supports is significantly smaller than 128MB. No idea if this is the case here.

darry wrote on 2025-04-26, 06:44:

ddoyle525 wrote on 2025-04-26, 06:35:

Horun wrote on 2025-04-26, 00:35:

Curious why you want to try and run 128Mb ram on a 486 board, max for true ms DOS is 64Mb iirc.

Just wanted to max it out to see how far I can push it. I've installed Windows 2000 successfully with 64MB RAM.

It might actually be slower with 128MB of RAM if the maximum cacheable range the chipset supports is significantly smaller than 128MB. No idea if this is the case here.

Windows 2000?
When you can avoid paging, no.
But I use 256 MB of RAM in my 486. Maximum cacheable area with 1 MB in write-through mode.

Disruptor wrote on 2025-04-26, 16:04:

Windows 2000? When you can avoid paging, no. But I use 256 MB of RAM in my 486. Maximum cacheable area with 1 MB in write-throug […]
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darry wrote on 2025-04-26, 06:44:

ddoyle525 wrote on 2025-04-26, 06:35:

Just wanted to max it out to see how far I can push it. I've installed Windows 2000 successfully with 64MB RAM.

It might actually be slower with 128MB of RAM if the maximum cacheable range the chipset supports is significantly smaller than 128MB. No idea if this is the case here.

Windows 2000?
When you can avoid paging, no.
But I use 256 MB of RAM in my 486. Maximum cacheable area with 1 MB in write-through mode.

In the case of software that would otherwise need to use a swap file, more RAM is always better. But for most people here the primary use case for a 486 is not running something like Windows 2000. Making Windows 2000 faster at the expense of making practically everything else slower might not be optimal for running 486 era software under DOS (depending also on how significant the slowdown would be, of course).

If OP's board can cache all 128MB of its RAM, there would obviously be no issue.

I tried one last pair of 64MB Crucial modules and it still would not work, so I decided to just leave it at 64MB. Those same Crucial modules worked great in my EFA 4DMS-HL3G 486 mobo so that helps.
I appreciate all the assistance.
--David

Second update - I figured it out. I was able to get it to work with 128MB RAM with a Diamond Speedstar Pro SE card but on some games the graphics were glitchy.
So I tried a generic Cirrus GD-5428 VLB card and numerous graphics errors appeared - even the Energy Star logo was all messed up. So I removed the memory module in SIMM slot #2 and - success! No more glitches.
It turns out the issue is SIMM slot #2 is bad on this MOBO because regardless of what memory stick I use in that slot it always fails. However I can use either stick in SIMM #1 just fine, no errors.
I'll have to live with 64MB RAM instead of 128MB but that is more than enough for legacy OS's.
I'm not sure why some video cards were more forgiving, but I can consistently re-produce the error and resolution every time with this generig GD-5428 card.
Phew!

Oh, well, it is VLB.
I remember I have at least one VLB graphics card which places its LFB at 64 MB.
So I'm unable to put more than 64 MB into this machine. I think the LFB was slightly below 64 MB, so the limit was somewhere at 48 or 56 MB. But I'm uncertain about this.

You may check the LFB address range of your VLB graphics cards.

And on some motherboards like my PVI 486 SP-3 I was not able to install both 128 MB modules. That board was limited to 192 (224) MB in fact.

It may be a case that you need to add an extra DRAM wait state to run 128MB.

I have a 386DX board that runs 0WS at 12MB but needs a CAS wait to run 16MB.