[Beowulf] ECC

[Reuti]

Am 05.11.2012 um 17:50 schrieb Douglas Eadline:

> --snip--
> 
>>> 
>>> More interesting is the ECC discussion.
>>> 
>>> ECC is simply a requirement IMHO, not a 'luxury thing' as some
>>> hardware engineers see it.
>> 
>> Depends on your computational model.  Would you rather spend money on ECC
>> or on more processors?
>> ECC comes at a cost in speed as well.  There is some non-zero time
>> required to compute the syndrome bits and do the correction on the read.
>> Sure, you can pipeline it, but there's some extra latency inevitably
>> added.
>> 
> 
> I find it interesting that many users thought GPU's could not be
> a research tool unless they had ECC memory. I have one associate who
> turns it off because they get 10% better performance on their
> Amber runs.

Turned if off in the BIOS or installed non-registered memory? With my tests I couldn't see any difference in execution time whether the installed ECC memory is switched off or on (or even which type of error correction I set up in the BIOS). Comparing registered and non-registered memory would be a more understandable difference in execution time.

Several CPUs also slow down memory access if many DIMMs are installed, so it seems to be better to use larger and hence fewer memory modules - which might be more expensive though.

-- Reuti