Hello,
I will be buying one of these motherboard for my workstation soon and
was wondering whether all 4 DIMM slots can take DDR400 memory in
full speed DDR mode?
I need 2GB of RAM and was planing to go the 4x512MB routes intead of
2x1GB mainly because of price.
I am asking because right now I use an K8V which has 3 slots advertised
as DDR by ASUS, yet only the 2 blue ones take DDR, the other one doesn't
AFAIK.
For the A8V, read this article. If using 4 DIMMs, the Command Rate is
set to 2T. If using 2 DIMMs, the Command Rate can be set to 1T. This
makes a difference to memory benchmarks. As far as the other DIMM
timings go, there doesn't seem to be any significant limitation. The
manual doesn't have a table listing limitations, and neither do
socket 939 processor datasheets that I've looked at.
Socket 939 motherboard review:
http://www.anandtech.com/mb/showdoc.aspx?i=2128
Socket 939 datasheet - memory controller page 13
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31411.pdf
The K8V has a table of limitations, and to use three double sided
DIMMs, it says the memory bus should be run at DDR200. That will make
a visible change to the performance of the board. Running 2 x 1GB
at DDR400, in slots 1 and 3, is the alternative. For best results,
the 1GB modules should not be "stacked" - the module should use
64Mx8 chips, so that the loading is no heavier than a double
sided 512MB module. Kingston and Crucial have the right kind of
modules. Corsairmicro.com offers some 1GB modules now also.
Samsung has been making 64Mx8 chips for more than a year, but it
has taken a while for them to show up at retail.
Remember, in both cases, the memory controller is inside the processor
and is not in the Northbridge. You cannot blame the memory population
rules on the motherboard design - the way that memory works in
this case is a function of the processor. for example, AMD claims that
the Newcastle processor has better memory drive characteristics, and
as newer versions of processor come out, the memory population rules
for the bus can make minor improvements.
AMD has been pretty cagey about its processor information. Table 1
in the K8V manual, is actually a table that was in an Athlon S754
datasheet published by AMD. But AMD was so ashamed of their design, that
they removed that table of information from subsequent versions of the
datasheet (I didn't keep a copy, so now the motherboard manuals
are the only evidence I've got).
S754 review - no K8V - Abit example shows 2 x DDR400, command rate 1T
http://www.anandtech.com/mb/showdoc.aspx?i=2063&p=3
Abit KV8 Pro 2 of 2 possible Dimms running DDR400
Chaintech VNF3-250 3! of 3 possible Dimms running DDR400
Epox 8KDA3+ 2 of 3 possible Dimms running DDR400
Gigabyte K8NSNXP 3 of 3 possible Dimms running DDR400 (tweaked)
MSI K8N Neo Platinum 3 of 3 possible Dimms running DDR400 (tweaked)
(
http://www.anandtech.com/mb/showdoc.aspx?i=2036&p=6)
Now, based on that review, perhaps your K8V might be able
to do better than the table in the manual shows. If you already
have the third stick of memory, then by all means test it, as it
might actually work at DDR400. As one of the boards in the above
review downclocked the memory bus when three DIMMs were detected,
you might need to enter the BIOS and set the memory bus to DDR400
manually. An extra 0.1V of Vdimm wouldn't hurt while testing
either.
HTH,
Paul
