Computing > Embedded Computing

SRAM PC133 - double sided vs single sided - detected half capacity?

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DiTBho:
I have several SRAM PC133 sticks: some are single-sided, some are double-sided, but each stick is 256 MByte.

Those single sided are correctly detected as 256MByte ram
Those double sided are detected as 128MByte ram

I fail to understand: why?!? Any idea?

If it's a firmware problem (u-boot), I can try to fix it :-//

oPossum:
Page 19 to 30

Note how the chip selects /S0 to /S3 are used. The double sided module probably requires /S1 and /S3 (in addition to /S0 and /S2).

David Hess:
Exactly, each side counts as a "rank" and the memory controller may only support 2 instead of 4 ranks, or 4 instead of 8 ranks.

rsjsouza:
Your post reminded me of how many times I assembled computers in the 1990s that had this and many other pitfalls - the motherboard/northbridge could be very particular in the types and models of components being used. It is amazing how so much of this knowledge quickly fades away...

DiTBho:

--- Quote from: rsjsouza on August 12, 2021, 11:53:48 pm ---It is amazing how so much of this knowledge quickly fades away...

--- End quote ---

Yesterday I contacted a RAM supplier who has a shop on eBay to find out if they can supply PC133 ram modules; talking to him ... he said that in the 2000s they had employees who sure know about my problem, but they are all retired and the information is lost without them.

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