On 14 Dec 2001, at 4:57, Philip Whittington wrote: > I'm sorry to trouble GIMPSers with what might be more of a computer question. I > am using an Athon Thunderbird 1.3GHz and 256 MB of 133 MHz (DDR) Ram. > > My computer has always emitted a high pitched squeaking noise when processes > like GIMPS start, and also when I do things like use the scroll wheel of my > mouse etc. Recently the computer started hanging randomly on certain tasks (not > GIMPS). After having taken the RAM down to 100MHz the high pitched squeak and > the hanging has stopped.
The most likely reasons for the "squeak" are: (a) some sort of mechanical resonance, perhaps involving the heatsink/CPU coupling, driven by magnetic linking from the "undertones" of CPU activity. Unless the noise is LOUD this is most probably harmless. (b) possibly the power supply is having difficulty providing sufficient current. Switched mode power supplies usually operate "supersonically" (around 50 KHz) but the frequency can be dragged down into the audible range by excess current draw. This would cause a squeal. Now a Tbird system does draw more current when the FPU is very active i.e. when Prime95 is running, but this should persist whilst Prime95 is running, rather than being transient as the program starts, as your message suggests. (?) Excess current draw would tend to cause system instability, getting worse as the smoothing capacitors age rapidly due to running under heavy strain. If your PSU is less than 250W or not marked as "Athlon approved" (see the AMD website) then I'd reccomend changing it for a 300W+ AMD/P4 approved PSU. Changing the system bus from 133 MHz to 100 MHz will underclock the system substantially (1.33 GHz will run at only 1 GHz) which will have the effect of reducing the current draw. Even changing the memory bus from 133 MHz to 100 MHz leaving the system bus at 133 MHz will reduce the load since the FPU will be inactive some of the time - the memory bandwidth is in any case inadequate to keep the FPU fully occupied, cutting the memory bandwidth by 25% obviously doesn't improve matters! > > 1) Will the hanging have any impact on the credibility of what PRIME95 finds - > I am around 86% through a L-L Test? Might be OK. Try running the full selftest, or the torture test. If these show no problems (despite the system hanging occasionally) you should be allright. In any case there's not much point in aborting 86% of the way through. Suggest you switch to DC assignments (after finishing this one) until the problem is sorted, though. > > 2) Can anyone shed light on whether it is my ram at fault or something on the > motherboard? (sorry, I realise this is not really GIMPS related) More likely M/B rather than RAM. Some Abit KT7s have weak smoothing capacitors, though others seem to be fine. This may depend on having an adequate PSU and/or adequate CPU cooling - the caps which blow are those next to the CPU, which therefore run hot if the CPU is inadequately ventilated. You might want to check out the memory using Memt25 but I doubt you will find a problem. If it is a PSU / smoothing cap problem, expect it to get worse, slowly at first but eventually getting so bad that the system won't boot. Repair is impractical; replacing the M/B will fix the problem temporarily, but it will recur, sooner rather than later, unless the PSU is upgraded. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
