Sunday, November 11, 2007

Heat, Speed, & Sound


Mr. Tobias Schonherr pointed out an error in my assembly of this new computer. Thank you Mr. Schonherr! I had misinterpreted the Intel manual on the DP35DP motherboard, and unwittingly installed the two memory modules in single-channel mode rather than dual-channel mode.

As I understand it, dual-channel mode enables the CPUs to make two requests on memory at one time, increasing overall memory throughput. See below. First the memory modules before and after, then the resulting Windows Experience Index before and after. The computer recognized 4 Gb of memory in each case, but you will notice that the memory sub-index jumped from 5.6 to 5.9, now as high as any other element of the system and higher than the dual-processor CPU.
Before After
Memory as originally installed Memory correctly installed
Original Windows Experience Index New Windows Experience Index


Modern computers contain a host of self-monitoring devices, temperature monitors in particular. I installed the Intel Desktop Utilities, which takes advantage of those devices to provide readouts and to raise an alarm if some device goes outside its limit.

A few days back I returned to my computer to find an alarm on the screen. The CPU had exceeded its temperature limit of 68 degrees C for several minutes, going as high as 69 C (156 F). I downloaded a system-exerciser program called HeavyLoad and ran the CPU test, which is a repetitive graphics application, and the CPU temperature jumped right up to 70 C, CPU fan becoming very audible. Oops - problem.

I wondered if the thermal transfer between the CPU and its heatsink was OK. I had removed the heatsink once to re-check that the CPU was correctly loaded in its socket, thus disturbing the termal transfer compound. Also I had never felt good about the seating of the clips that hold the heatsink to the motherboard.

So I removed the heatsink once again, removed the old thermal transfer compound, and applied Arctic Silver compound in its place, evening it out with a credit card. Replacing the heatsink atop the CPU cover, I tried very carefully this time to apply equal pressure on all of the mounting clips, hearing a satisfying little click at each corner, an assurance that the heatsink is held down squarely. I also disconnected the internal case fan from motherboard control and connected it to full voltage so that it will always run full speed. It's noiseless anyway.

Good results! The following measurements were made with HeavyLoad executing its graphic application (about 60% CPU utilization), and the hole pattern in the back of the case blocked, thus forcing air to come all the way through from the front). In each case, temperatures were allowed to settle for at least a quarter of an hour. The CPU fan is automatically controlled from the motherboard:

  C C C C C Fan
Max allowed 68 85 119 109   RPM
Exhaust fan LOW (silent) 60 48 62 66 53 1467
Exhaust fan MED (audible) 60 49 62 66 50 1345
Exhaust fan HI (whoosh) 59 47 62 66 50 1348
Fan LOW, no HeavyLoad 40 41 63 66 53 927

I wish it were cooler still, but the CPU is now well within specifications. Further, the speed of the rear exhaust fan doesn't seem to make much difference in the temperatures, though it makes a lot of difference in noise. So I'm leaving the fan on low until there is a problem.


I admit that my hearing isn't what it once was, but this system is so quiet that I can't always be sure I'm hearing it. A very low rumble from the disk drives is about all there is, and only when they are busy. But when the forced-air-furnace comes on I just can't hear it at all. I LOVE that! Now about that furnace ...

1 comment:

Steve Gauss said...

Well, Don, once again grat minds run in a similar vein. I have a new case on my desk with the WD SATA and a CD-R/W installed and just waiting for the motherboard to show up. I also chose the Core 2 Duo 6750, but went with a Gigabyte motherboard. I need the legacy ports, as my HP-4L laserjet is still running just fine.
I've built several computers and usually don't save much money, but do get exactly what I want.
I also chose Windows XP over Vista. I have a Vista machine, but none of my web cams work and there's no driver for my scanner. I have several pieces of software that still work fine, but I would need to re-purchase them to work on Vista. Since I also use linux quite a bit, my old computer will go to upgrade my linux system.
While it is pretty amazing whatis available now compared to the 21-MX and even the HP A900 (I think I made it to 9Mb of memory), I also recall that I was completely running the telescope and collectingits data in 256Mb of memory and 15Mb of disk space.
One of the activities I spend a lot of time on is at You can see underwater pictures of the reef that I took with a webcam sealed into a long pipe - one of the ones that doesn't work under Vista.
Regards to you and Ardis.
Steve Gauss