System Builder Marathon: Overclocking

Overclocking The Medium-Cost System

Now we move on to the medium-cost build, with some very serious hardware compared to the low-cost machine :

The primary reason for choosing the Asus P5N-T motherboard was its attractive feature set, however this particular board does not have an excellent overclocking reputation. ASUS has released a new BIOS recently so we were eager to see if the P5N-T could perform adequately and perhaps even excel.

It turned out the P5N-T was very accommodating and allowed us to operate the Q6700 at 3.7 GHz with relative ease. At this speed we found the machine was a little unstable ; further investigation showed we were reaching temperatures of 67 degrees Celsius while running the Prime95 stress test.

The problem is that CPU instability can often be cured with higher voltage, however the instability was likely caused by heat generation - in which case higher voltage will only make the problem worse. Our Cooler Master HyperTX2 was doing an excellent job of air cooling at these high frequencies and voltages but we suspect we were simply reaching the limits of what reasonable air cooling can accomplish. Without a liquid cooling option, we pulled the overclock back a bit to 3.6 GHz, a not-insignificant 1 GHz over-clock over stock. Perhaps with water cooling we might have been able to pull more out of the Q6700, but since we went with air it highlighted the fact that a cheaper Q6600 CPU with similar G0 stepping would probably have made it to similar over-clocked speeds for a much lower price.

The voltages we ran were still somewhat high with the vcore and northbridge set to 1.5 volts. The front side bus was set to 360 MHz with memory running in linked synchronous mode.

Our Geforce 8800 GTX was willing to over-clock past 625 MHz core/1000 MHz memory, but there was some system instability that once again had us pulling back the over clock a little. We finally settled on 590 MHz core and 990 MHz memory, which gave us a slight performance bump but nothing to write home about.

Now that you know what we’re running and how we ran it, let’s see how it performed :