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How to decode this warning about memory from my motherboard manual?

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First post, by Kahenraz

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The manual for my AN430TX has a warning about memory modules. Does this mean that I shouldn't use any double-sided modules (16 chips), or is it warning about a certain kind of memory module with 16 chips?

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I am interested in buying these memory sticks but they have 16 chips on them. Are these ones that I should avoid for this board?

I am trying to stay within the 64MB cache limit, but I keep finding 32MB sticks with 16 chips on them. I could use a single 64MB stick, but I prefer the aesthetic of having all of the memory slots populated.

This reminds me of the era of "high density" and "low density" memory, which never made a whole lot of sense to me.

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Edit:

I just found sticks with 4 chips on either side but are still labeled 4M x 64. This is so confusing.

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Reply 1 of 2, by dionb

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JEDEC SDRAM spec says that chips should be 8 or 16b wide, so an unbuffered DIMM needs 4 or 8 chips for single rank (64b wide) / 8 or 16 chips for dual rank (2x 64b wide). However it was cheaper to make 4b wide chips, which led to some manufacturers making non-JEDEC-compliant DIMMs with 16 of these 4b wide chips, which physically had chips on both sides of the DIMM but were logically just a single rank DIMM.

Intel chipsets - such as the i430TX on this board - stuck rigidly to JEDEC specs and could not work with these non-standard DIMMs. Other chipset vendors were more flexible, most famously Via, leading to these DIMMs to be labeled 'Via only' - even if 'won't work with Intel would be more accurate'

So DIMMs with 16 chips can work perfectly well on this board, so long as they are double rank DIMMs with 16 8bit wide chips, not single rank DIMMs with 4b wide chips

How to tell? Look up the data sheets of the chips on the DIMMs. If they are "x8" they are good, if "X4" then not so. Chips on 32MB DIMMs with 16 chips should have with 2Mx8 structure. 4Mx4 would be bad.

Tbh I've never seen 16MB or 32MB DIMMs with X4 chips. The commonest were 16Mx4 chips on 64MB DIMMs and 32Mx4 on 128MB DIMMs.

Reply 2 of 2, by rasz_pl

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There was a lot of "AMD only" DDR3 ram coming out of China couple of years ago. I can still see plenty on auction sites. Probably similar story there.

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

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