Show your pictures of 50ns and 60ns memory modules please. I have feeling this is EDO modules not compatible with your motherboard. You can use FPM modules with 60ns or 50ns. I had bought 8 pieces of 60ns FPM 4MB modules and they work well and is needed for my compaq computer that needs 60ns FPM.

Second, memory are just that, memory and vanish when turned off. The motherboards requires firmware stored on one IC installed on your motherboard, not memory modules.

Cheers,

Are the other memory modules also parity? With the working module in, try checking in the BIOS to see if the parity check is enabled. If it is, try disabling it, then trying other modules.

I think that could be. I hear of EDO, FPM, etc.. but all I know is that they are RAM that fits so it should be true. Are typical 486 memories EDO? They are SIMM with the same pins exactly, that's all I know. So, all I need to do is buy some SIMM with similar pins but they should be FPM. Also,. does motherboard not support EDO? I thought those were standard memory that work on any of my other 486 motherboards.

486 boards in general are FPM memory. Not EDO.

This is important to provide your photos of your not compatible memory modules so we can tell you what you actually have. This is not the motherboard issue.

One more thing, if IBM-made FPM memory modules with 9 chips, that also not compatible, IBM made with 12 chips are compatible, I'm referring to 72 pin type. I have to investigative that what reason why they happens.

Anything else we need your photos of these memory modules of yours.

Cheers,

Here,

but you are right, these modules might not work with the motherboard (I was confused and thought something about BIOS because of the conflicting message, even though I know BIOS is in the ROM and not the RAM,. but the real problem and the message should be invalid memory modules or something).

I read in the manual now "Support SIMM type: 1Mx36, 2Mx36, 4Mx36"
I thing this Mx36 designation is for this FPM memory? And Mx32 is the EDO.
Somehow I didn't know or forgot the 486 had the FPM first and then the other kind later (which are for Pentium but worked on another motherboard with slower 486)
Anyway,. I think that's the issue, just the message confused me, and didn't know it's the case. I thought if it fits it must work. I will buy some FPM from ebay or something.

x36 only mean, that you need PARITY memory, it mean 3 or 9 or 18 memory chips, not 2, 8, 16.

EDO will only work with some few newer UMC based motherboards. Maybe some more. For 486 only use EDO.

Optimus wrote on 2021-06-03, 06:13:

Here, […]
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Here,

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but you are right, these modules might not work with the motherboard (I was confused and thought something about BIOS because of the conflicting message, even though I know BIOS is in the ROM and not the RAM,. but the real problem and the message should be invalid memory modules or something).

I read in the manual now "Support SIMM type: 1Mx36, 2Mx36, 4Mx36"
I thing this Mx36 designation is for this FPM memory? And Mx32 is the EDO.
Somehow I didn't know or forgot the 486 had the FPM first and then the other kind later (which are for Pentium but worked on another motherboard with slower 486)
Anyway,. I think that's the issue, just the message confused me, and didn't know it's the case. I thought if it fits it must work. I will buy some FPM from ebay or something.

That's an EDO RAM module. It won't work with your motherboard (and most 486 motherboards). Get FPM RAM and you'll be good to go.
I also have the same board and it behaves EXTREMELY weirdly with EDO. At first it seems like it works (and it can even try and boot sometimes), but it will never actually work properly.