[rescue] weird Opteron 865 / Tyan 4882 problem

Patrick Giagnocavo patrick at zill.net
Tue Jul 14 20:35:29 CDT 2009

Hoping someone can give me some advice on this system:

4x Opteron 865 (dual core CPUs)

As you know, each Opteron has its "own" RAM using its on-board memory
controller.  Each CPU has 4 slots.

All CPUs are fully populated with 4x1GB ECC DIMMs, except for CPU1.

Conditions under which system will hang:
CPU1 with no RAM
CPU1 with 4x DIMMs

Conditions under which system will boot fine:
CPU1 with 2x DIMMs

BUT the system does not see the RAM as existing!  That is, I see 12GB
RAM at bootup and when the system is running, not 14GB as it should be.

My thinking is that either:

1.  CPU1 is partially busted (specifically its memory controller) and
should be replaced


2.  There is a problem with the DIMM slots itself, like maybe a resistor
 or some other electrical channel problem.

My main concern is reliability - I want to use ESXi v4 on this beast and
put it in colocation... I can get by with 12GB provided the system
remains stable, and performance even going with UMA instead of NUMA is
still pretty decent.

Any ideas?  Suggestions for further testing?



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