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Although ATI felt the pressure to keep its Radeon HD 5970 under 300W for the sake of those folks with 750 and 850W power supplies, the card was originally designed to hit 5870 frequencies and deal with the corresponding thermal load that would have created. Thus, you have hardware on-board well-suited for overclocking, yet technically overkill for the 5970’s stock specifications.
There’s the 400W-capable vapor chamber-based cooler, for example. ATI also uses a programmable PWM fan controller able to monitor 12 different points on the board. Screened ASICs, higher-binned memory chips, and beefier digital VRMs are all part of the effort to infuse extra headroom “similar to what you get on a Black Edition Phenom II,” AMD says. That last part is a bit ironic; anyone willing to spend $600 on graphics should be looking to an overclocked Core i7 to help balance it out.
Complementing the purportedly more-scalable hardware is a bit of special software. The voltage tweaking utility comes first. ATI’s reference example took our GPU from 1.05V to 1.1625V and our memory from 1.1V to 1.15V. We’re curious to see if third-party board vendors choose any voltage levels above or below those levels. Second, ATI caps the core and memory clocks much higher, letting you choose up to 1,000/1,500 MHz frequencies. We were able to get our sample stable at 925/1,300MHz.
I’m not a huge fan of running overclocking numbers on vendor-supplied launch samples for fairly obvious reasons. However, overclocking is supposed to be a big part of what makes this board unique, so without further ado…
All of our numbers here are at 1920x1200 (or 1900x1200 in the case of Crysis), with game-specific details listed on the y-axis. As you can see, in some cases, overclocking has a profound effect on performance—from between 30%+ in Far Cry 2 to just under 2% in the very CPU-bound Left 4 Dead.
Unfortunately, hitting Radeon HD 5870 frequencies (850/1,200 MHz) requires upping the 5970’s voltages in order to achieve stability.