Paul, I had a very bad experience with the NVidia chipsets. Another user of the mersenneforum confirmed those results.
Could you tell us what timings you get running 4 primality tests together and the corresponding FFT sizes ? Your hardware specifications : model of CPU, its running frequency, memory... Jacob Visser > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Paul Charlton > Sent: 2007-12-24 18:12 > To: 'The Great Internet Mersenne Prime Search list' > Subject: Re: [Prime] Benchmark question re: multiple cores > > 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. > 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. > 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"] > 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. > 6) get the latest nForce drivers from NVidia download site. > > -----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
