According to several leaked AMD slides, the upcoming HD 5970 Hemlock card should be quite an overclocker.

In a slide titled 'Massive Overclocking Headroom', AMD boasts core clocks in excess of 1GHz with unlocked Overdrive. We're a bit skeptical about the 1GHz claim, but it should be close. The HD 5970 features a vapor chamber cooler capable of dissipating 400W, as well as an enclosed thermal shroud and a massive fan with a fully vented exhaust, so it should be able to cope with the extra heat.

As we said yesterday, max board power draw is rated at 294W. Even while it's idling, the HD 5970 will suck 42W worth of fossil fuels. That's just a tad less than an HD 4650 under load.

Nevertheless, Hemlock will be the fastest card around for the next few months, and if you're after top notch performance, power consumption is probably not your top priority.