X79, ram, and f@h
Thought this was interesting, while fooling around last night with a little overclocking I borrowed a couple sticks from my X79 rig to run some benchmarks on P67. I left the rig to fold overnight with only the two remaining sticks, and woke up this morning to a significant drop in PPD.
The socket 2011 machine is a 3960X@4.7Ghz paired with 4x4Gb of G.Skill 2133 ram cas 9. So 16GB of memory running quad channel.
I've had nothing but P6904 units for weeks so I'm pretty familiar with it's performance. (Numbers are running Linux client via VirtualBox.)
TPF is around 51mins, PPD ~114,00
So overnight the rig was running in dual channel, 2X4GB of the same 2133 c9 ram, memory usage was under 6GB in total so it wasn't maxed out.
TFP rose to 61 mins, PPD sunk to 95,000
This was a bigger hit than I would have thought going from dual to quad channel, maybe there's something else going on that I'm missing, but thought I'd share.
Having said that, I share your surprise. I figured part of the reason why memory bandwidth made as much of a difference on G34 is because each processing thread needs its own address space, so a large MP system would depend more heavily on RAM performance. Your findings, though, would suggest it has more to do with the quad-channel bandwidth itself being particularly agreeable to FAH. This is indeed interesting. Thanks for sharing!
I know that it's an issue with a AMD G34 setup, regardless of the number of processors in it so it makes sense I guess.
edit: Ninja'd by DT
Interesting...I would have said prior to your post it makes no real difference.
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