Safe Overclock: 3.8 GHz (FSB1600)
The next, most logical step is FSB1600, which equals the system speed being used by the Core 2 Extreme QX9770 (400 MHz base clock speed). Although the enthusiast systems run on the X48 chipset, the P45 can also support FSB1600 speeds easily, although Intel did not officially release the chipset for this speed. However, the plethora of motherboards being promoted as FSB1600-capable illustrate the existing overclocking margins.
We had to increase the CPU voltage from 1.35 V to 1.385 V to hit 3.8 GHz on FSB1600 (400 MHz base clock speed), which wasn’t a problem. However, the system wasn’t stable at first—Prime95 crashed after a few seconds of operation. We increased the microcontroller hub/northbridge voltage to 1.25 V to be sure it wouldn’t fail during overclocking, and we further increased the processor voltage to 1.405 V. This allowed us to operate the system at up to 3.9 GHz, although we decided to stick with 3.8 GHz to ensure reliability. Additional core clock speed of 100 MHz won’t deliver much extra performance, but it will increase the risk of system crashes.
Great Performance, Increased Power Consumption
We used the Core 2 Duo E7200 at 3.8 GHz core clock speed and FSB1600 system speed in our test labs for several days, and found it a rather quick workhorse. We benchmarked the processor at stock speed (2.53 GHz), at 3.4 GHz and at 3.8 GHz, and included the Core 2 Duo E8500 for reference.
The power level of the overclocked system wasn’t great, however, as the overclocked processor idle power went from only 91 W for the entire system to as much as 102 W at 3.8 GHz for the overclocked Core 2 Duo E7200. The peak power changed even more: while the system running the E7200 required only 121 W peak power, it went to 149 W at 3.4 GHz and as high as 170 W at 3.8 GHz. This represents a 40 percent increase in system power consumption. The same system running a Core 2 Duo E8500 showed peak power of only 134 W; it was outperformed by the overclocked E7200 by a considerable margin.