We used the same platform for our overclocking experiments as we used for performance tests. However, instead of the standard boxed cooler, we installed a much more efficient Scythe Infinity with a 120-mm fan rotating at 1,800rpm.
The nominal Vcore of our processor was 1.2V and we decided to attempt overclocking it without increasing this voltage setting.
Intel traditionally removed the overspeed protection of expensive processors for computer enthusiasts. Core 2 Extreme QX9650 was not exception. So, we managed to get this CPU to run stably at 3410MHz obtained as 10 x 341MHz. Unfortunately, at higher frequencies the CPU failed to pass Prime95 stability test.
Anyway, quad-core processor overclocking to 3.4GHz without raising its Vcore is a very decent result. Although some Kentsfield processors with G0 core stepping could do something like that, we shouldn’t disregard their higher nominal voltage.
The second part of our tests was performed with the CPU Vcore increased to 1.5V. I would like to point out that Yorkfield’s lower heat dissipation does help a lot during overclocking: even with the voltage raised significantly the tested quad-core processor didn’t get overheated and didn’t fall into thermal throttling.
We managed to overclock Core 2 Extreme QX9650 to the maximum frequency of 4068GHz without losing stability. It was obtained as 12 x 339MHz.
So, the new processors can easily exceed 4GHz bar with air cooling system. Isn’t it great evidence how significant the frequency potential of the 45nm cores is?
By the way, our test CPU running at 4068MHz remained within acceptable thermal range all the time. Its maximum temperature didn’t exceed 85єC, and its minimal temperature in idle mode equaled 43єC.