dual channel ram configuration for dual processors on Asus K8N-DL

Im making a system using the K8N-DL and 2x Opteron 265s. I want to get
the full potential out of the board with bus speeds and utilizing dual
channel ram. The mobo manual states for dual cpu you need this ram bank
configuration: DIMM_A1+DIMM_A2=DIMM_B1+DIMM_B2=DIMM_A3+DIMM_B3. Does
this mean you need 6 sticks of ram? or 3 or what? I was planning on 6x
512 sticks but I read something that said using 6 sticks will degrade
ram performance. I just want to buy the right stuff. Can someone
advise me please? Thanks

 

Wow, that description in the manual is just terrible!

If it was my board, I would put two sticks of RAM on each
processor. I would buy four identical sticks. They could be
512MB each (for a 2GB system total) or 1GB each (for a 4GB system
total). I don't know if there are issues with going larger than
that or not, as the processor contains the memory controller,
and I haven't read any accounts of using a 2GB or 4GB sized
registered DIMM. (The AMD 26094 document contains more info,
but is not a user friendly document.) Using two sticks per
processor, is the highest speed configuration for the
memory clock. Using four double sided sticks on one processor,
usually means a (small) speed penalty.

http://forums.2cpu.com/showthread.php?t=63239&page=31&pp=30&highlight=k8n-dl

The way the original Athlon64 was described, is not really
dual channel in the most flexible sense. AMD started with
the concept of either 64 bit wide memory, or 128 bit wide
memory. When you install a DIMM on one channel, the corresponding
DIMM slot on the other channel has to be populated, for the
two DIMMs to be fed identical address/control info, and for
the two of them to function as a "128 bit wide" uber-DIMM.
That is what dual channel means to AMD.

Based on that premise of operation, A1=B1, A2=B2, A3=B3 would
be the best rule to follow to allow 128 bit wide operation.
If you populate A1, then you should also populate B1. And so
on.

To use four sticks, then A1=B1 and A3=B3, would be one
solution. Or A2=B2 and A3=B3 is the second solution.

By means of the interconnected Hypertransport busses, it is
possible for one processor to access the memory of the
other processor. In fact, there are some dual socket AMD
motherboards, where the second processor has no memory slots,
and thus the second processor "leeches" off the memory belonging
to the first processor.

940 pin memory population rules are on Pg. 184 (table 49). I
notice quad rank (whatever that is, 36 chips per module?) are
mentioned, with an appropriate speed penalty for their use. If
you stick with two double-sided registered DIMMs per processor,
you can stay at DDR400.

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26094.PDF

You might dig up more info on forums.2cpu.com. Search engine:

http://forums.2cpu.com/search.php

And finally, this article discusses various interleaving options
on multiprocessor Opteron boards.

http://www.digit-life.com/articles2/cpu/rmma-numa.html

Hope that gets you started,
Paul

 

I built one, the RAM instructions in manual are slightly incorrect. The
pairing is wrong. If u follow the pairing plan u end up with non-dual
channel. You need to match the colours for each 2 sticks of RAM.

The first 4 slots are for CPU 1. The last 2 slots are for the CPU 2.

Remember that there may be a limitation for the amount of RAM that the OS
can use. For example if its a server and you're using Windows Small
Business Server 2003 then its 4GB limitation.

The manual is probably the worst manual I've ever seen for a RAID enabled
motherboard. It doesn't even have a section about the RAID setup, not even
1 page or 1 paragraph.