Athlon 64 939 motherboard RAM size/speed data - big fibs

[macclesfield]

I am looking at the latest 939 motherboards from the likes of MSI, Gigabyte etc for Athlon 3500+ use.
I would like 1 GB of RAM now, and maybe 2Gb in a year and 4 Gb in 2 years, all at DDR400 min speeds.

The memory "sizes / dual channel / DDR speeds / ECC or not" data is not as specified on the websites and in the product pdf's.

Typically headline specs say upto 4Gb DDR400 dual channel. Can this be done ? not on your nelly !

Maker #1 says : max is 2 Gb for DDR400, and also says "If you use 2pcs DDR400 the speed will auto downgrade to DDR333 - Use only one 1pcs of DDR400. This is part of the AMD K8 CPU spec."

Maker # 2 says : Can't do 4Gb at all, only 3.5 Gb, so please only use 3Gb !

AMD's site and data is very vague about this, but the Bios guide says :

1) 4 ECC dimms max, or 3 dimms unbuffered max (or maybe only 2)
2) CL2/CL2.5 dual channel memory only possible up to 166 MHz
3) DDR400 CL2/CL2.5 is only single channel
4) DDR400 CL3 is OK dual channel

Another little gem is the 3500+ clock of 2.2 Ghz means that DDR333 runs at 157 not 166 Mhz.

One good point is that it appears that the latest revisions on the cpu accept 2T timing for unbuffered chips (not as the original chips 7 to 11T values.

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OK so what are the true RAM configuration maximums ?

Does anyone have the true data ?

 

[Peter]

The CPU _does_ do large DIMMs. However, 32-bit address space is only 4 GBytes total, and your PCI and AGP devices have to live somewhere in there too. That's why you won't see all of your 4-GByte RAM array as long as you're in a 32-bit OS. If you're using a 64-bit operating system, you'll get the "missing" bit back, remapped to beyond the 4-GB border.

 

[Steve]

Originally posted by: macclesfield
OK so what are the true RAM configuration maximums ?

Does anyone have the true data ?

JEDEC specs state one DIMM of DDR400 per channel, two of DDR333, and three of DDR266. That's provided you're using unbuffered RAM. Registered RAM allows for more high-speed DIMMs per channel.

People have been lucky enough to get unbuffered RAM working beyond the JEDEC spec (DIMMs per channel), and sometimes the makers reflect this in their board specs to attract the overclocking crowd.