Overclocking

The impressive results of the previous test demonstrated that the new core of the Pentium D processors became “cooler”. This gives us some hope that the frequency potential revealed during overclocking will also get better. However, we couldn’t complain about the B1 Presler core stepping. During our tests of the Pentium Extreme Edition 955 we managed to overclock this CPU up to 4.26GHz with the regular air cooling only. This result was 25% higher than the nominal clock frequency of this CPU, which is a pretty impressive result for the top model in the family. But will the new C1 core stepping allow improving this result even more? Let’s find out now.

Before we pass over to the detailed description of our overclocking experiments, we have to point out that the dual-core Pentium Extreme Edition processors remain quite overclocking-friendly solutions. Intel doesn’t lock their clock frequency multiplier that is why we can overclock these processors not only by raising their bus frequency, but also by increasing their clock multiplier. This not only makes overclocking a lot easier, but also partially justifies for the higher price of these products.

The test platform we assembled for our overclocking session was built around ASUS P5WD2-E Premium mainboard based on i975X chipset. The memory subsystem consisted of two Corsair CM2X1024-6400PRO memory modules. Besides that, the platform featured NVIDIA GeForce 7800 GT graphics card and Western Digital WD740GD HDD.

Note that we didn’t aim at any extreme overclocking results. Therefore, we used a mass air cooler that is available at stores today - Zalman CNPS9500 LED. So, you should keep in mind that more advanced cooling systems may allow you to reach much higher overclocking results.

Our Pentium Extreme Edition 965 processor worked just fine at the frequencies up to 4GHz without any additional Vcore increase.

If we continue our overclocking experiments with the Vcore increase, the results will be even better. We have already said a few times that Presler based processors overclock very well by raising the core voltage. Therefore, we continued our overclocking experiments with higher Vcore settings of 1.375V. In this case we managed to increase the clock multiplier to 16x and achieve the 4.26GHz frequency. Note that the processor was absolutely stable and didn’t switch to thermal throttling.

Further multiplier increase caused the complete loss of system stability. The same effect resulted from the FSB frequency increase over 270MHz. when the FSB speed was set between 267MHz and 270MHz, the system could still work fine, however, the “hardest” SnM and Prime95 tests would still cause some problems. So, we regard the 4.26GHz value as our final and maximum overclocking achievement.

Is it high or not? On the one hand, this frequency is 15% higher than the nominal frequency of the Pentium Extreme Edition 965 processor, and it indicates that this processor family hasn’t yet exhausted its frequency potential. However on the other hand, we have already reached 4.26GHz when we experimented with Presler B1 core stepping processors before. And it means that despite all the enhancements of the C1 core stepping, such as lower heat dissipation, the frequency potential didn’t grow any bigger. In other words, overclocker’s shouldn’t really hope for any breakthroughs to come with the new Intel CPUs on Presler C1 core stepping.