Luke Welsh wrote: > At 04:36 PM 12/21/2007 -0800, John R Pierce wrote: > >> its also possible that running all 4 cores full tilt is causing some >> thermal throttling... no matter HOW good your heatsink is, the CPUs can >> develop local hotspots internally under intense workloads and >> automatically slow down select execution units. >> > > Perhaps worthwhile to try underclocking? >
Upon more thorough re-reading, the thread George pointed out on the forums contains a report that the nVidia chipset may be the culprit here. http://www.mersenneforum.org/showthread.php?t=6937 S485122 from Belgium points out: <QUOTE> In my experience the NVidia chipset is no good for running multiple memory intensive applications concurrently. Here are benchmarks done with all parameters equal except the motherboard : QX6700 at stock speed, 6400-C4 memory...) P965 chipset (Asus P5B-E) One core used : 31 Two cores on different dies (0 and 2 for instance : 33 Two cores on the same dye : 34 Three cores : 37 Four cores : 42 NVIDIA 650 SLI (Asus P5N-E SLI) One core used : 34 Two cores on different dies (0 and 2 for instance : 41 Two cores on the same dye : 39 Three cores : 58 Four cores : 74 </QUOTE> Now, my memory is a bit better than his (8500-C5D rather than 6400-C4), but otherwise its essentially the same system. When he did the same tests I did on the P965 chipset (all other things being equal), his iteration time was only up 35% over a single core. On the nVidia, all other things being equal, his increase was 217%. My increase was from 0.050 to 0.116 or 232% increase, right in line with his findings. I use the nVidia chipset. (Yes, I have the most recent flash, as of last week). It would seem to me that if I really wanted to get back to 0.06x iteration times, I might want to swap out the motherboard, and then re-tune the overclock. (UGH, what a heavy job in a watercooled system -- I'm not sure it's *that* important to me! I'll have to think about that one....but in the end I'll probably bite the bullet and cross-grade to the Asus Maximus Formula Intel X38-based motherboard since the only reason I went with the nVidia was for the possibility of using SLI in the future... which I don't do for now.) In any case, it would seem to be "problem source located", if not problem solved. Thanks for everyone's feedback! Jeff _______________________________________________ Prime mailing list [email protected] http://hogranch.com/mailman/listinfo/prime
