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Overclocking

System Builder Marathon, December 2010: $500 PC
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When the time came to tinker outside of spec, our first order of business was to determine if the dormant processing core could be successfully unlocked. We had a stable fourth core in September, but this time our system refused to even boot as an Athlon II X4. The motherboard’s design, unfortunately, made resetting the system a bit tedious, as accessing the clear CMOS jumper requires removal of the graphics card.

While unlocking was a failure, our Athlon II had a good deal of headroom for increasing core speed. The chip’s VID (Voltage ID) was 1.3 V, as opposed to the September machine's 1.4 V. Once again, the motherboard overvolted a bit beyond that. At stock voltage, stability was found beyond 3.4 GHz.

We only took the CPU up to 1.4 V in the BIOS, which CPU-Z reported as 1.432 V at idle and 1.464 V during load, finally settling for a respectable 3.875 GHz (250 * 15.5). This Mushkin RAM was found to have little headroom, so the 250 MHz reference clock worked out for keeping our RAM within spec (at DDR3-1333). Maximum available CPU-NB frequency was 2500 MHz, but we settled for 2250 MHz due to the motherboard's cooling and lack of adjustable CPU-NB voltage.

The Sparkle GeForce GTX 460 also had a decent amount of headroom for increased frequencies, and the quiet cooler was effective for overclocking without overriding the auto fan settings. Starting at a reference 675 MHz core and 1350 MHz shaders, our card topped out at 835/1670 MHz, respectively. We didn’t push the GDDR5 memory all the way to its breaking point, calling it quits after raising it from 900 MHz (3600 MT/s effective) up to 1060 MHz (4240 MT/s). These frequencies were then dialed back to 823/1640/1050 (4200) during our overclocked set of benchmarks.

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