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Assembly And Overclocking

System Builder Marathon, Dec. 2009: $1,300 Enthusiast PC
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This system was very straightforward to assemble. The NZXT M59 affords a lot of space for the price, and even the fairly large Radeon HD 5850 cards slipped into the Gigabyte motherboard with ease. The case also offered a reasonable amount of space for cable management. The result, pleasantly, was a quick setup.

Overclocking

First off, we think it's important to mention that for all intents and purposes, our Core i5-750 CPU is a 2.8 GHz part, even though it is advertised as a 2.66 GHz CPU. This is because it constantly ran a turbo multiplier of 21x for a 2,793 MHz clock speed even when all four CPU cores were stressed. The higher speed can be attributed to the processor's Turbo Boost settings, and so long as you're able to keep the CPU within its thermal/power bounds, it'll run at 2.8 GHz all day long.

Overclocking the Core i5-750 without the budget to afford a good aftermarket cooler is an exercise in temperature control. Unlike most overclocking experiences we've had in the past, we found that this CPU was so eager to overclock with stock voltage that it quickly reached 100 degrees Celsius when set to a relatively mild 3.6 GHz speed. The CPU had legs to go much further, but we pulled back considering, what those temperatures can do to hardware. We wanted a real-world overclock that wouldn't melt the box after a month of use.

Since our nemesis was temperature and not a CPU limitation, we actually “under-volted” the processor in order to reduce heat. With the CPU reduced to 1.15V from the stock 1.25V setting, we were able to keep our 3,612 MHz overclock without breaking the temperature barrier during Prime95 runs.

The fact that the CPU was willing to clock this high while under-volted really speaks to its potential for a much higher overclock with proper cooling, but we'll have to leave that to the lucky winner of the contest for this machine.

As we've mentioned previously, we'll first run our factory-overclocked XFX Radeon HD 5850s at reference speeds to simulate a garden-variety model of the cards that would fit within our budget. To get the overclocked numbers, we've pushed the speed as far as the BIOS will allow to 775 MHz core/1,125 MHz memory. This is ludicrously close to the factory overclock of 765 MHz core/1,125 MHz memory with which this overclocked edition card comes, so the overclock very closely represents what the XFX Radeon HD 5850 Black Edition is like in stock form.

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