Too bad we don't have a photograph where we can see of what kind and how many of chips your DIMM modules are made from.

As for the 440 BX I know that this chipset has limitations as far as the memory chips are organized.

Edit:
It seems your MT8LSDT3264AG-133B2 module has Micron 48lc32m8a2 chips which seem to by 32 M x 8 chips.
It should carry 8 chips then, which is single sided.
As my experience has shown single sided 256 MB DIMM modules in 440 BX systems always show half of the capacity.
Please try double sided 256 MB DIMM modules instead.

AshleyK wrote on 2023-04-08, 07:26:

Hello everyone […]
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Hello everyone

I bought a Lucky Tech P6BX2 motherboard with a i440BX chipset to finally be able to play around with my Slot 1 CPUs.
But i have ran into an issue, it doesn't detect any 256 mb sdram dimms properly , instead reporting them as 128mb. The motherboard's manual also says that it does support up to 768 mb of ram in a 3x256mb config, but no luck for me. Have tested with 3 different dimms, that i have previously verified on a Compaq Skt370 board to be 256MB, all reporting 128MB on the PII board.
Is there anything i missed or i can do about it? Any help would be appreciated.
Thanks in advance.

Chipset memory controller limitation, you need to find 256MB sticks that have chips on both sides of the stick to have a chance the memory controller recognizes the full 256MB capacity.

It comes down to how large the memory chips are on the stick and how they are structured in there, ran into this myself a while back.

You need DIMMs with 2 rows of 128Mb DRAM chips. In one of my 440BX system I have 4 x Micron 16LSDT3264AG-133E1 DIMMs and all 1GB works.

I just checked a well known auction site and Micron 16LSDT3264AG-133E1 are cheap enough

You need 256mb modules with memory ic's on both sides of the stick. Any 16x8, 7.5 ns should work. The ones you have, at lest the MT one is single sided (32x8).

It's what the others said. 440BX (and also LX etc) won't work with DIMMs that have a too high chip density. If the chip density is twice its max, it will see only half the memory.
So it's quite unlikely something is actually broken 😜
It's just a compatibility issue.

Short story long, that is the caveat with BX chipset. The following explains in details:
https://web.archive.org/web/20180103032407/ht … ram_bx_faq.html

384MB RAM will be more than sufficient for 440BX. Windows 98 can't use more than 512MB without a patch anyway. You will benefit from a faster CPU more than from more RAM in your case. Buy a Katmai 600 or PII 400.