Overclocking
The results of our performance tests turned out exactly as we have expected them to be and honestly, not very exciting ?this is evidently not the main intrigue of the day. It is much more interesting to see how well the new processors will overclock, taking into account that they are built on the new G0 core stepping that is expected to boast better frequency potential. However, on the other hand, the increased to 333MHz FSB frequency may cause new Core 2 Duo to overclock slightly worse than their predecessors. Their frequency multipliers are quite low and hence they are more likely to hit against the unpleasant FSB Wall.
To clear things out, we decided to take a closer look at the frequency potential of the new processors that arrived into our lab. We used the same platform on Asus P5K Deluxe for our overclocking experiments as we used for our performance tests. This mainboard suits perfectly for overclocking CPUs with 1333MHz bus because it maintains excellent stability at high FSB frequencies. Since the clock frequency multipliers of our processors, unlike Core 2 Extreme, cannot be increased beyond their nominal value, we had to overclock by raising the FSB speed. During our overclocking experiments we used Zalman CNPS9700 LED processor cooler. The system stability was checked with SP2004/ORTHOS utility.
The first one to get to the testbed was Core 2 Duo E6850 processor. By raising its Vcore to 1.5V we managed to get it to work at 3.79GHz (9 x 420MHz) without any stability issues.
So, the top model of the three dual-core newcomers allowed a 26% frequency boost without much effort and with the traditional air-cooling involved. It is a pretty good result for the fastest CPU in the family. For instance, Core 2 Extreme X6800 processor we tested earlier (based on B2 core revision) could work stably only at 3.6GHz, not more.
The second overclocking experiment was devoted to Core 2 Duo E6750 with the nominal frequency of 2.66GHz and 8x default clock multiplier. The maximum FSB frequency we managed to achieve for this processor by raising its Vcore to 1.5V was 461MHz.
So, the tested Core 2 Duo E6750 hit 3.69GHz, which is 38% higher than its default spec frequency. This could be a very good achievement if it hadn?t been for one thing. The 461MHz FSB frequency we achieved turned out to be the notorious FSB Wall, because we failed to overcome it with reduced clock frequency multiplier. In other words, the new processors with 1333MHz bus and G0 core stepping are not free from the FSB Wall problem. To our regret.
The third CPU, Core 2 Duo E6550, will definitely be of great interest to overclockers. This is the youngest CPU on G0 core stepping. Its nominal clock frequency is 2.33GHz, it works with 7x multiplier. That is why you can only succeed in overclocking this processor if you have a high-quality mainboard that can push FSB to 500MHz and up. Asus P5K Deluxe that we used is one of these boards. We managed to overclock our processor to the maximum of 3.57GHz with the Vcore increased to 1.5V.
To hit this frequency we raised the FSB to 510MHz thus getting a 53% frequency increase above the nominal. Note that in this case we didn?t hit the FSB Wall but simply exhausted the processor capabilities.
So, new Core 2 Duo processors with 1333MHz bus overclock pretty well. The new G0 core stepping obviously proved up to the mark here.
