Power, Heat, And Efficiency
ATI’s Radeon HD 4890 graphics cards require enormous quantities of power, so it’s not difficult to understand how the $2,500 system’s 3-way CrossFireX configuration has higher demands than the $1,250 build’s 4-way Radeon HD 4850 combination. With half the CPU and GPU cores of the mid-priced system, the $650 budget PC appears a true miser.
The $650 machine also runs cooler at full load than its more-expensive competitors, in spite of its small aluminum retail-boxed CPU cooler. Surprisingly, the $1250 machine with four graphics cards sports the lowest GPU temperatures under load. This is likely a result of better case cooling than the $650 PC and cooler graphics cards than the $2500 PC.
With performance increases that are greater than power consumption increases, overclocking improved the efficiency of $650 and $1,250 builds. By comparison, the already-inefficient $2,500 PC became even less efficient when overclocked, its aggressive CPU voltage increase providing only moderate performance gain.