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PC100 Memory difference

Chuck(G)

Chuck(G)

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I've got a couple of sets of Micron PC100 registered ECC SDRAM, both Micron.

One set is made up of MT18LSDT3272G-10EE1 (256M) DIMMs.
The other is made up of MT18LSDT1672G-10EB1 (128M) DIMMs

One (the 128M set) works in a system I have, but not the other. Other than the size, what's the difference? Anyone have a clue?
 
Are the 256 MB ones double sided? I remember in the days of SIMMs and SDRAMs, some motherboards would not accept memory modules with chips on both sides. I don't know the technology behind, but in the choice between two memory modules of the same capacity but one had all chips on the same side, people usually would try that one first.
 
carlsson said:
Are the 256 MB ones double sided? I remember in the days of SIMMs and SDRAMs, some motherboards would not accept memory modules with chips on both sides. I don't know the technology behind, but in the choice between two memory modules of the same capacity but one had all chips on the same side, people usually would try that one first.
Click to expand...

They're actually both double sided. They appear nearly identical--they're both Micron and the 128MB ones are a bit shorter than the 256MB ones. The spec sheets are nearly identical but for the 32x72 vs. 16x72 organization. Could it be that the BIOS doesn't like them?
 
I looked up a 256MB DIMM for the 440BX chipset and got this:

256MB 168-pin PC100 CL2 2-Bank 16-chip 16x8 SDRAM DIMM
256MB SDRAM, PC100, CL=2, Non-Parity, 100Mhz, 3.3v, 168Pin DIMM, 32Meg x 64 - Major Brand
 
Have you tested the 256MB DIMM in another motherboard? Perhaps the contacts just need to be cleaned?

Anyway, a 16 (or 18 in this case) chip 256MB DIMM should work in a BX.
 
It does work in a different 440BX motherboard. But no mixture of the 128M and 256M DIMMs (mixed or alone) sees the 256M. I'm going to go prowling for a BIOS update.
 
Chuck, I'm anctiously waiting to hear from you again. I still find it strange they won't work together. All I can think of now is perhaps it's the different memory densities that make them not work together. Some motherboards don't particularly like having to deal with different density memory, I try to avoid mixing where I can
 
Could the motherboard have multiple memory banks, and if you have more than two slots it would help to insert them into different banks? Oh well, you said both motherboards are based on the 440BX chipset so probably the technology behind will be the same.

Who said computer hardware got easier to install and use through the years? It seems this kind of modern-ish hardware can have just as many culprits as truly vintage computer hardware does. In 20 years time, enthusiasts of the day will find all those generations of hardware just as bothersome. :)
 
I had a motherboard, an ASUS A78XVX iirc., that would not accept the cheaper high density memory. If you stick a stick of that in there, it would immediately smoke and die. I did so, not knowing this. The motherboard survived the ordeal, but that RAMstick was instantly fried.

Point is a motherboard can be picky.

That said, I've never seen a machine that took PC100 or PC133 complain in the slightest about a RAMstick, unless the RAMstick was bad. I'd wager one of your two sticks has some corruption issues in it - try a memtest with each in the machine alone.
 
Updated the BIOS and the PC sees the 256M memory (as shown on the system inventory screen); just refuses to use it. There are 3 DIMM slots. If I put 128+128+256 in, the 256 shows as 256, but total memory is 256. If I try 256+256, the system won't boot. If I try 256+256+128, I get 128. Mind you, they don't get flagged as having errors.

Pretty strange, huh? Might be something in the SPD EPROM, I'm thinking. Anyone know of a utility to read/modify the things?
 
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