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Overclocking

System Builder Marathon, March 2011: $500 Gaming PC
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Our Phenom II’s VID (Voltage ID) was 1.35 V. And, as we’ve come to expect, ASRock's M3A77DE overvolted a bit beyond that, reaching 1.40 V under load. Stock temperatures during Prime95 testing were already 52 degrees Celsius (core) and 54 degrees Celsius (socket). In order to allow a  little breathing room for warm summer months, the goal was to maximize our overclock with very little temperature increase. To do this, the CPU needed to be undervolted.

A 0.05 V reduction in CPU voltage (to 1.300 V in the BIOS) was good for 3.4 GHz, resulting in the same load temperatures as the stock processor. Bumping up to 1.325 V increased our CPU temperature 2-3 degrees alone, leaving no room to explore higher speeds.

As we've seen in the past, there wasn't much to gain from overclocking our budget-oriented memory. Memtest 86+ flagged frequent errors at 1633 MT/s, despite bumping DIMM Voltage to 1.65 V and further loosening timings. At 1296 MT/s, the machine wouldn’t boot at CAS 7, so final timings were 8-8-8-24 1T at 1.59 V. Increasing memory bandwidth would require either swapping in more expensive RAM or leveraging the flexibility of a multiplier-unlocked Black Edition processor.

Overclocking Sapphire's Radeon HD 6850 can be summed up in just one word: disappointing.

I fully expected the card’s 850 MHz BIOS limit to prematurely cap our GPU core frequency when using AMD Overdrive. Instead, I ran into major shader artifacts appearing well below that limit. The maximum stable overclock was a paltry 820 MHz for the core, while the memory was good for 1130 MHz (4520 MT/s).

These figures were then lowered to 800 MHz and 1100 MHz to assure stability through the duration of testing. This is a rather insignificant overclock that pales in comparison to the Sparkle GeForce GTX 460 used back in December.

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