I tried to force the Alliance ones into the slots, but my motherboard won't recognize them(Repeated beeps at boot up). What could be the problem?

It looks like this may be the answer: "Some manufacturers of non x86 workstation released 72pin SIMMs not compatile with PCs. Notably IBM made some 40 Bit SIMMs for their RS/6000 line and hp modules from hp 9000 series are not compatible with PC-hardware. "

http://www.vogonswiki.com/index.php/72-pin_SIMM

The photograph doesn't show the chip inscriptions on the second SIMM well enough to determine its specs (even whether it's EDO or FP or something else entirely), and it looks pretty unusual. It's not impossible it is a regular 32b SIMM, but I'd want better pictures to be sure.

The first one is a pretty regular 72p 32b SIMM with 4Mb EDO chips, so if it only has chips on one side it is a 4MB non-parity module and if it has chips on both sides, it's 8MB non-parity.

But isn't this a simpler issue? The MediaGX has a 64b memory bus, so needs SIMMs installed in pairs - electrically identical pairs. If the second SIMM isn't identical to the first, it won't work. Given the six visible chips on the SIMM, I strongly doubt it will be electrically identical to the first one. In which case no POST - which is what you are seeing.

dionb wrote on 2023-07-11, 08:28:

The photograph doesn't show the chip inscriptions on the second SIMM well enough to determine its specs

Here is the clear version:

dionb wrote on 2023-07-11, 08:28:

The first one is a pretty regular 72p 32b SIMM with 4Mb EDO chips, so if it only has chips on one side it is a 4MB non-parity module and if it has chips on both sides, it's 8MB non-parity.

But isn't this a simpler issue? The MediaGX has a 64b memory bus, so needs SIMMs installed in pairs - electrically identical pairs. If the second SIMM isn't identical to the first, it won't work. Given the six visible chips on the SIMM, I strongly doubt it will be electrically identical to the first one. In which case no POST - which is what you are seeing.

Sorry for not making sense. I should've said I have two of them each, the picture posted earlier is intended to show the difference. They are all 2-sided 72pin 16mb EDO rams. I don't know the exact model number of my original ram, but they work.
When inserted in pairs, the BIOS recognizes them as 32mb in total.
The Alliance won't be recognized by the machine, when inserted(forcefully) in pairs there are repeated beeps, no video.
The interesting part is when I pair these two different rams, the BIOS recognizes only my original one. The total amount of ram is 16mb. Then throw a "memory test failed" error.

They have almost the same size with only about 0.2mm difference. Note the round opening in middle of the connecting fingers.

GunKneeNeon wrote on 2023-07-11, 11:44:

[...]

Sorry for not making sense. I should've said I have two of them each, the picture posted earlier is intended to show the difference. They are all 2-sided 72pin 16mb EDO rams.

I strongly doubt that. 16MB SIMMs have an odd power of 2 chips onboard, so 2 64Mb chips or 8 16Mb chips.

Even with a good pic I can't figure out what chips those things with "4MX3E2K5DJ-6DD" are - "4M" or "4MX" isn't any regular vendor code.

But the Alliance chips are clear enough and they are 4Mb chips, not 16Mb, so those 8 chips visible in the pic amount to 4MB. If there are 8 more of the same type on the back, that's an 8MB SIMM, not a 16MB SIMM.
(note capitalization - when discussing memory it's vital to keep bits and Bytes clear and separate)

I don't know the exact model number of my original ram, but they work.
When inserted in pairs, the BIOS recognizes them as 32mb in total.

That suggests that they are 16MB SIMMs. With the ununsual number of chips, I would assume that they are parity SIMMs. That may be important later on...

The Alliance won't be recognized by the machine, when inserted(forcefully) in pairs there are repeated beeps, no video.

Two options:
1) the SIMMs are dead.
2) the SIMMs can't support memory settings on the board.
(I'm ruling out 3 - they are obscure non-standard SIMMs, as unlike the unknown ones they are completely bog-standard 4MB/8MB non-parity units)

Note the difference in parity: if you have parity check enabled, those SIMMs with Alliance chips won't work. If they work in another system but not here, that would be my first suspicion. Boot with the working SIMMs, check if parity is enabled in BIOS. If so, disable it and you might find the SIMMs with Alliance chips suddenly do work.

The interesting part is when I pair these two different rams, the BIOS recognizes only my original one. The total amount of ram is 16mb. Then throw a "memory test failed" error.

The SIMMs are of different size and configuration, that is never going to work.

They have almost the same size with only about 0.2mm difference. Note the round opening in middle of the connecting fingers.
size1.jpg
size2.jpg

Not convinced that difference is real - it looks like the second SIMM is shifted to the left in its entirety (see left edge) rather than any difference in the key slot.

dionb wrote on 2023-07-11, 12:37:

But the Alliance chips are clear enough and they are 4Mb chips, not 16Mb, so those 8 chips visible in the pic amount to 4MB. If there are 8 more of the same type on the back, that's an 8MB SIMM, not a 16MB SIMM.

I never made them work, the seller told me they are 16MB. Maybe he cheated me.

Boot with the working SIMMs, check if parity is enabled in BIOS. If so, disable it and you might find the SIMMs with Alliance chips suddenly do work.

I've checked the parity setting, it's disabled.

The SIMMs are of different size and configuration, that is never going to work.

I thought it would output no video at all in this case.

Not convinced that difference is real - it looks like the second SIMM is shifted to the left in its entirety (see left edge) rather than any difference in the key slot.

Oops, my measurement is faulty, but see the picture with the memory slot. The Alliance one won't fit the slot, I have to force it in. I have other two different pairs of rams, they all fit naturally just like my unknown 16MB EDO ones.

Line up two SIMMs facing each other with pins edges touching. From the pictures with ruler it looks like hole is one pin off