On 22 Dec 2001, at 18:55, Paradox wrote: > As I email'd previously, I have an Intel Pentium 4 1.9 GHz with PC800 > RAM in an Intel D850GBC motherboard running Windows 2000. Even with no > other programs running, and a minimal of services, (100% of cpu > dedicated to prime95), I get approximately 0.180 seconds/iteration. > According to the benchmark on mersenne.org, I should be getting closer > to 0.143 seconds/iteration.
Interesting, that's almost exactly 80%. > I suspect that my Pentium 4 may be engaging > its built in "Thermal Monitor" feature, which is mentioned on Intel's > website, without extensive documentation (as far as I can find). The > Thermal Monitor is a temperature sensor inside the Pentium 4 which > detects when the processor is getting too hot and reduces system > performance in order to compensate. Most BIOSes have a setup which allows you to change the throttle ratio (the realtive clock speed when throttled) and the threshold temperature at which throttling is applied. If you find a throttle ratio of 80% then you've got it. If you find the throttle ratio is set to 50% then the throttling theory is wrong, you'll have to find the cause elsewhere - try using the Task Manager to see what else is running. > I have noticed > using my motherboard's temperature sensor (different from the internal > P4 sensor), that Prime95 raises my CPU temperature from approximately > 90 to 95 F to exactly 124 F, which is immediately below an indicated > threshold. This makes me suspect that the P4's Thermal Monitor > is engaged and could be causing the performance decrease. I have looked > for, but have not found, a way to detect whether or not the Thermal > Monitor is infact being activated. I want to make sure this is the case > before taking drastic actions on my CPU's cooling system. Any help would > be appreciated. 124F = 51C ... sounds too hot for the system board sensor ... 51C may be OK for the CPU sensor, though. Mind you I'd expect the threshold to be at 50C or 55C rather than 52C. If your system board sensor really is reading 124F then you almost certainly have a problem with case ventilation. Is the case fan(s) (if fitted) running? Is the fan in the PSU running? You don't have a strange problem like the one I found last week, where the PSU fan was reversed, thereby blowing pre-heated air into the vicinity of the CPU cooler inlet? If you can't spot a problem like that, try adding another case fan. Most good cases have fittings for relatively cheap (think $5) 8cm cooling fans. Normally you fit these so that they blow into the case; it is usually obvious if this is wrong i.e. the fan is mounted so that it is adjacent to the CPU in such a position that, if it were to suck rather than blow, it would be getting a high proportion of its air from the CPU cooler "exhaust". If your case doesn't have fittings for an extra case fan, you can get a "HD cooler" (two or three 40mm fans in a plate which will fit a 5.25" drive bay). Try one of those. You can also get extractors which fit an expansion slot; these are useful for cooling e.g. graphics cards, but also help keep the rest of the case volume a bit cooler. Disabling thermal throttling by setting the throttle ratio to 100% or moving the threshold temp way up is also acceptable _provided the system passes the torture test_ after changing the parameters. In fact this _might_ be the best way to fix the problem, since your m/b may have a minor problem (possibly duff BIOS software - did you check for an upgrade?) causing throttling irrespective of sensed temperature. You might also want to try the torture test with the system clock temporarily wound up a couple of percent and/or a case fan disconnected; if the system is stable & error-free under those conditions, it should be OK in normal service. If you try this please watch the system carefully & return to normal if it shows signs of instability or logs more than a very occasional error in the torture test. Mild overheating will not cause permanent damage but prolonged, severe overheating might. Seasonal felicitations Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
