Kahenraz wrote on 2021-08-24, 02:39:

Either I don't understand how these numbers work or I'm getting bad information. The listing I bought this from listed the memor […]
Show full quote

Either I don't understand how these numbers work or I'm getting bad information. The listing I bought this from listed the memory as 32MX64. But all of the sticks that I currently have with that identifier are double sided.

I assumed that this would be double sided as well but it is not.

Is this memory actually 32MX64 or something else? Is this something I can calculate with just the size of the module and the number of memory chips on it?

I already know that this memory is in fact double-rank (2RX4 according to EVEREST). I thought that this would be enough for my 440EX to accept it as 256MB but it only shows up as 128MB so having chips on both sides DOES matter in this case.

I can confirm that all 256MB modules I have tried that are 2RX4 recognize at full capacity and they are labeled 32MX64 with chips on both sides. I do not have any double sided 256MB memory with only single rank to compare.

IMG_20210823_222347.jpg

IMG_20210823_222317.jpg

If you are looking for 256MB SDRAM DIMMs that will be recognized at full capacity by a 440BX board, start by considering only modules with 16 chips as only those have a chance of working at full capacity (there are other constraints) on the 440BX .

I suggest that you read this : https://web.archive.org/web/20180103032407/ht … ram_bx_faq.html

Specifically, this should answer your 32MX64 question, in part at least .

1 Q: My vendor lists a 256MB module as PC133, 32Mx64, will it work?
2A: Sorry, I have no idea. "32Mx64" refers to the EXTERNAL organization of the module, meaning it has 32 million addresses of 64 bit (=8 byte) each. Multiply 32 million with 8 and you get your ram size -> 256MB. This unfortunately means EVERY 256MB module (at least  168-pin Dimms) will be organized in this way, because the size is (obviously) fixed and the bus width (64bit) is given by the ram interface and thus fixed too. You need to know the INTERNAL organization of the module (the organization of the ram chips).

Yep.

A 256MB module with 8 chips must (as 8b=1B) have 256Mb chips. i440 chipsets can handle max 128Mb per chip, so this module will get detected as 128MB.

If you want 256MB to work on that board, you need a 256MB DIMM with 16Mx8 128Mb chips. Note that 32Mx4 128Mb chips won't work at all.

The way to tell is simple: don't look up specs of the DIMM, look up specs of the chips themselves, in this case the HY57V561620CT-H. Its datasheet will tell you what it is: https://pdf1.alldatasheet.com/datasheet-pdf/v … 561620CT-H.html

In this case it's a somewhat unusual 16Mx16 256Mb chip (as opposed to the more usual 32Mx8) . Unusual as that makes an 8-chip DIMM with chips physically only on one side still electrically double-sided (dual rank), as the 8 chips together have 2x64bit width. However being double-sided doesn't help you if the chip density is still too high, as it is here.