Paul Charlton wrote: > Few more thoughts, then we have exhausted my repertoire on the facts at hand > ... > > 1) Make sure that you get the latest bios upgrade for the motherboard ... > they keep tweaking voltage and timing parameters. >
This was done about 2 weeks ago, just prior to when I started overclocking after I moved to a new cooling system. Downloaded fresh at the time from nVidia. > 2) do not manually set the RAM parameters...set all memory speed/voltage to > auto/default, then choose the SLI Memory setting for 0% OverCLOCK mode, > which enables the motherboard to set speed/voltage from the EPP in the ram > chips. > This was unstable. I had to manually lock it in at stock timings 5-5-5-18-2T for stability. > 3) disable all of the "spread spectrum" timings > 4) disable all of the CPU auto-speed selection option [ie: disable "CPU > Thermal control" and "Intel Speedstep"] > These have long been done. > 5) if your memory is still unstable, I would suspect northbridge overheating > ... the evga board comes with an aux fan for the northbridge for use when > watercooling the cpu. > That fan is installed and operating. > 6) get the latest nForce drivers from NVidia download site. > This was also done at the time I flashed the BIOS. However, I'm not using nTune to mod the clocks. I'm doing that at the BIOS level, rebooting and changing there. Jeff > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Jeff Woods > Sent: Monday, December 24, 2007 8:01 AM > To: The Great Internet Mersenne Prime Search list > Subject: Re: [Prime] Benchmark question re: multiple cores > > Paul Charlton wrote: > > >> You never stated which motherboard chipset/northbridge is in your system. >> > I > >> have essentially an identical system (Nvidia 680i), but with CPU x12 >> (3200MHz), air cooled, and get substantially better results. The Corsair >> dominator I have run well @ FSB 1066/linked, with 2.2v for memory banks. >> Unlinked memory speeds are measurably slower unless they hit a "sweet" >> timing ratio with the FSB. >> >> > > > I thought I had stated the chipset in a later Email, but the mobo is an > eVGA 122-CK-NF68, an nVidia 680i: > > http://www.evga.com/products/pdf/122-CK-NF68.pdf > > I have been unable to achieve any stability running the RAM linked at > 1066, even with no multiplier overclock. Any effort to set the RAM bus > speed to "linked, 1:1" (i.e. 1066) resulted in system instability at > worst, or SUMINP != SUMOUT errors at best. > > > > >> What will help a lot if you have not done it (the mailing list is silent >> > on > >> this issue) is to set "cpu affinity" for each of your P95 threads (can do >> from task manager with a right click) >> >> > > > This should not be necessary, given that I have it set CPU affinity > directly from the "Advanced" -> "Affinity" menu option within each > instance of P95. However, I just now altered the affinity settings in > Task Manager, carefully matching each PID's affinity to its instance's > internal "Advanced -> Affinity" settings. This did help not help in the > slightest. > > Thanks for your efforts, in any case. I'm going to try migrating to the > Intel X34 chipset to see if that helps. > > Jeff > > > >> -----Original Message----- >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On >> Behalf Of Jeff Woods >> Sent: Friday, December 21, 2007 9:38 AM >> To: The Great Internet Mersenne Prime Search list >> Subject: [Prime] Benchmark question re: multiple cores >> >> Hello All, >> >> My second (and hopefully last) question after returning to the GIMPS >> fold. I've never unsub'd from the mailing list, though, and haven't seen >> this question come across.... >> >> I have a Quad Core QX6700, which is my first multi-core system, and my >> first overclocked system. It has just finished up P-1 stage 2 factoring >> and begun LL tests on each of its cores. >> >> http://www.mersenne.org/bench.htm >> >> The benchmark page above says that a Core 2 Quad QX6700 should be >> running about 0.0569 per iteration on a 2560K FFT. I assume that's at >> default clocks. >> >> My system seems to be averaging less than half that, between 0.105 and >> 0.131, depending on which core.... and I can't figure out why. What >> should take 24 days is going to take 60 days at this rate. >> >> The following may be irrelevant, but I'm wondering.... >> >> The native 2.66 Ghz CPU is overclocked to 3.47 Ghz, with Vista 64 (and >> Prime95's 64-bit version) so I can have full access to all of 4 GB of >> very fast RAM. The RAM is Corsair Dominator PC2-8500 (800 Mhz native, >> 5-5-5-18-2T) and for extra memory bandwidth I've overclocked the RAM to >> 1000 Mhz. The CPU overclocking is all done via multiplier (10X -> 13X) >> and voltage, and the RAM overclock is done by configuring the >> motherboard's RAM speed to be unlinked from the FSB, then manually >> increasing the RAM speed to its max stable level of 1000 Mhz. I did not >> alter the FSB speed at all, since my RAID controller doesn't like FSB >> speed tweaks. Nor did I alter the memory timings, leaving them at the >> native 5-5-5-18-2T. The system is sufficiently cooled (liquid, >> sustaining 59C-63C at 100% load on all 4 cores) and passed overnight >> torture testing without throwing up errors. >> >> With the above tweaks, the system throws up 12500 3DMarks, and scores an >> overall 5.9 on Vista's Experience Rating (the best one can score). It >> was scoring 5.8 prior to my increase of the memory speed from 800 Mhz to >> 1000 Mhz, so my bump should have boosted memory bandwidth. Alas, >> matching 1:1 and running the memory at 1066 Mhz (the native FSB speed of >> the system) is not stable. I can't quite push the memory that fast -- >> 1000 Mhz is where stability tops out. At 1066 Mhz memory speed, I start >> getting rounding errors after 3-4 hours of torture testing. >> >> Now, here's what I'm wondering. Is it possible that the source of these >> slower benchmarks is that tiny discrepancy between the FSB speed and the >> RAM speed? Would there be timing delays in running the memory just >> SLIGHTLY slower than the FSB that P95 doesn't much like due to its use >> of RAM for the lookup tables? >> >> Or, is it simpler than that? Am I perhaps bumping up against L2 cache >> thrashing, something that might be common on Intel multi-core machines >> that share a single L2 cache like this? (Nehalem, where art thou?) Is >> the benchmark listed simply what one core would do if it had exclusive >> use of the L2 cache while other cores were idle, and the lower iteration >> times are to be expected when all four cores are each working on their >> respective exponents, contending for a single L2 cache? >> >> This last theory seems to be supported by the fact that I paused all but >> one core and let it iterate on that one core with near-exclusive use of >> the otherwise idle system, and the iteration times fell dramatically, to >> 0.050 sustained and "best time" from the Options->Benchmark menu of >> 0.048. That's more in line with what I'd expect, given the benchmark >> pages showing a stock clocked QX6700 cranking at 0.0569, combined with >> my overclock. >> >> So, to cut to the chase, the benchmarks seem to be geared to exclusive >> use of the L2 cache, but in the real world that's not how I'd imagine >> most GIMPS users run P95 on a multi-core system. If my hypothesis is >> correct, wouldn't it be better to post separate benchmarks for "one core >> in use" versus "all cores in use", so that people's expectations aren't >> skewed by a benchmark table that doesn't represent typical use? >> >> Any guidance or experience would be welcome. >> >> Thanks! >> >> Jeff Woods >> Reading, PA >> >> >> >> _______________________________________________ >> Prime mailing list >> [email protected] >> http://hogranch.com/mailman/listinfo/prime >> >> _______________________________________________ >> Prime mailing list >> [email protected] >> http://hogranch.com/mailman/listinfo/prime >> >> >> > > _______________________________________________ > Prime mailing list > [email protected] > http://hogranch.com/mailman/listinfo/prime > > _______________________________________________ > Prime mailing list > [email protected] > http://hogranch.com/mailman/listinfo/prime > > _______________________________________________ Prime mailing list [email protected] http://hogranch.com/mailman/listinfo/prime
