Overclockability

They tested the overclockability of the Core i7-965 Extreme Edition and were able to achieve a maximum stable clock speed of 3.9 GHz at stock voltage, using only the stock cooler. That's an overclock of about 22 % over the stock clock speed of 3.2 GHz. The CPU temperature was quoted as 44 °C but the test system used a high-airflow case to achieve that low temperature.

DDR3 Memory Voltage

Intel confirmed the 1.65 V limit on memory voltage. According to Intel, the Core i7's memory controller is rated to support a voltage of 1.5 V but they allow voltages of up to 1.65 V for those who intend to overclock. However, that is the absolute limit. Going above that will very likely "fry" the memory controller and turn that expensive processor into a piece of useless paperweight.

Intel recommends that you do not overclock the DDR3 memory modules. The Core i7's triple memory channels, on-die memory controller and multi-level caches deliver such high memory bandwidth that there is very little performance benefit from using even higher-speed memory modules. To prove the point, they ran the test systems using only DDR3-1066 modules. See below for the performance results.

Cache & Memory Performance

Intel showed us a testbed running the Core i7-965 Extreme Edition processor with DDR3-1066 memory running on timings of 9-9-9-24. Here are the cache and memory bandwidth results :

As you can see, the Core i7's triple DDR3 memory channels delivered about 12 GB/s of bandwidth even using just DDR3-1066 memory modules. We will have more details on the caches in an upcoming tech report.

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