[Beowulf] Optimal BIOS settings for Tyan K8SRE
hahn at physics.mcmaster.ca
Thu Sep 7 06:44:00 PDT 2006
> What chipkill buys you is the reasonable assurance that if you
> have a long uptime and you get soft memory errors something will
> look at and correct the data before multiple errors have time to
true, but I think you mean scrubbing, not chipkill. from AMD's
bios-writers doc, chipkill actually just changes the ECC to
incorporate all 128b; the 'chip' part comes from the fact that
with 4x dram chips, the syndrome maps to a particular chip
(and all 4 bits from that chip can be corrected.)
this has been a useful discussion, because I hadn't previously
realized just what was the benefit (prevent accumulation of
multi-bit errors, proactively fix some singles) and cost
(a tiny amount of bandwidth, O(100KB/s).
> For performance I suspect you will see much more variation depending
> on the speed of memory in your system.
the max scrub rate (64B in 40ns) is 1.6 GB/s. that's a lot, but is
still lower than the bandwidth from even a single-dimm config.
(NOT to imply it's a sensible setting in that case!)
for my 8GB machines, I suspect a daily scrub (50KB/s per node)
will have undetectable overhead.
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