Did you tried let's say 32 and 64MB or you try some big SDRAM sticks like 128MB?
I actually had similar problem once and it turned out to be hardware error. Couple resistors near the ram slots on the mobo were torn.

All the SDRAM I have laying around are 64mb PC-100 sticks. I think my motherboard officially supports up to 128 or 256mb, something like that. It only has two SDRAM slots and I don't see anything physically wrong with the board.

I have a board with the same issue: Acorp 5TX52.
Works perfectly fine with EDO RAM, but is unstable with ANY SDRAM module I tried (and, boy, did I try A LOT of them, including various 16/32/64 MB PC100 sticks which are known to work fine on any other board).

Funnily enough, I have another similar Acorp board (5TX29) which is one of the best Socket 7 boards I've ever used. Not only does that one work fine with SDRAM, but it is 100% stable at 83 MHz FSB (running a Pentium MMX at 292 MHz).

I should mention that, even though my Acorp 5TX52 only works with FPM/EDO RAM, there's no noticeable performance hit when compared to SDRAM (as long as I use 60ns EDO sticks and set the correct timing in the BIOS).
It even works fine at 75MHz FSB (though 83 MHz is completely out of reach).

For me there is a performance difference. With Quake, I get 50fps with EDO RAM and 52fps with SDRAM (no sound, 320x200). Obviously stability is worth it over two extra frames, but it'd be nice. You also don't think the problem would be because I have PC-100 and not PC-66 sticks?

What motherboard do you have? If it's 430VX or TX based, then you might need older DIMMs, usually 32MB PC66 do the trick.

Garrett W wrote on 2021-04-13, 08:31:

What motherboard do you have? If it's 430VX or TX based, then you might need older DIMMs, usually 32MB PC66 do the trick.

Pretty sure it's one of those, yes. Maybe I'll have to look into acquiring some PC-66 RAM eventually.

bloodem wrote on 2021-04-13, 07:36:

I have a board with the same issue: Acorp 5TX52. Works perfectly fine with EDO RAM, but is unstable with ANY SDRAM module I trie […]
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I have a board with the same issue: Acorp 5TX52.
Works perfectly fine with EDO RAM, but is unstable with ANY SDRAM module I tried (and, boy, did I try A LOT of them, including various 16/32/64 MB PC100 sticks which are known to work fine on any other board).

Funnily enough, I have another similar Acorp board (5TX29) which is one of the best Socket 7 boards I've ever used. Not only does that one work fine with SDRAM, but it is 100% stable at 83 MHz FSB (running a Pentium MMX at 292 MHz).

I should mention that, even though my Acorp 5TX52 only works with FPM/EDO RAM, there's no noticeable performance hit when compared to SDRAM (as long as I use 60ns EDO sticks and set the correct timing in the BIOS).
It even works fine at 75MHz FSB (though 83 MHz is completely out of reach).

i dont remember the make of the board, but i had one with a Cyrix 6x86 and both sdram and EDO slots. It never worked well with sd ram, but fine with EDO and i've heard this a number of times, never sure what the reason was though

one of the many computers i let go, and now think i'd like to experiment with!

you probably have a 430VX chipset, which is the first intel chipset to support SDRAM. these are quite picky and supposedly need early "2 clk" design RAM. the safest bet would be to hunt for sticks with 96-97 date codes.

i do seem to remember being able to run PC100 in a TX board so those might not be as picky, but it could depend on the board as well.

So, I tried arranging my EDO sticks differently (they're four sticks with 2 sticks being one brand and the other two being another and I spaced them out like brand 1, brand 2, brand 1, brand 2) and making sure the BIOS was set to 60ns. Perhaps it was the former, the later, or both, but I got my 52fps on Quake with the EDO sticks. Perhaps I won't need to hunt for more SDRAM after all.

Garrett W wrote on 2021-04-13, 08:31:

What motherboard do you have? If it's 430VX or TX based, then you might need older DIMMs, usually 32MB PC66 do the trick.

It's not the speed but the chip density that's relevant in this case. You need a 32MB DIMM with 16 chips (16Mb each), not one with 4 chips, if using i430VX. i430TX is far less picky, it officially supports up to 64Mb chips (so 128MB DIMMs with 16 chips) and can work with 128Mb chips (256MB DIMMs with 16 chips), depending on motherboard implementation.

But OP, please clarify which motherboard you have, as otherwise we're just speculating.

At least in my case, the 5TX52 is a 430TX motherboard (just like the 5TX29), and it still doesn't work properly with any type of SDRAM, no matter the manufacturer or chip density (tried 16 x 8 MB, 16 x 4 MB , 16 x 2 MB, 8 x 2 MB, 8 x 4 MB) --> that's MegaBytes.
The motherboard officially supports any of these memory modules (and the 5TX29 works fine with any of them), but the 5TX52 is unstable with all. EDO, on the other hand, works like a charm.

I just attributed this behavior to a quirk that this particular motherboard might have (many Socket 7 boards have weird quirks, anyway, even those with Intel chipsets), so I just accepted it for what it is and went with EDO RAM (especially since there was literally no performance hit). Also, it was a chance for me to finally use EDO (with good reason) in a Pentium system, since all of my other ones have SDRAM 😁