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Sapphire Toxic HD 7970 GHz Edition Review: Gaming On 6 GB Of GDDR5

Clock Frequencies And Power Consumption: Gaming

We used the same three clock rates on the previous page for our gaming analysis: 1100 MHz (from the factory), Lethal Boost's 1200 MHz, and a static 1201 MHz.

The TDP-based frequency limiter didn’t kick in at all in our gaming workload, maintaining 1100 MHz and Lethal Boost's 1200 MHz. Part of this is due to Sapphire's aggressive cooling profile, which also makes the Toxic HD 7970 GHz Edition 6 GB quite loud.

One interesting attribute of Lethal Boost is that it extends the PowerTune limit to 50 percent instead of 20. Thus, we added this as another variable to test. Set to 50 percent, the card started jumping between 1100 and 1200 MHz. So, we fixed the clock rate at 1201 MHz.

Power consumption jumps quite a bit from 1100 MHz to the higher frequency settings. At 1100 MHz, we recorded about 204 W. The 1200 and 1201 MHz settings were a little higher, at 218 W. Stepping up to the 50 percent PowerTune setting increased consumption to 229 W.

Does this affect frame rates at all?

The higher frequencies barely make a difference in frame rates (at least, not enough to justify up to 20 percent more power consumption). Really though, this is the same thing we saw in our review of Gigabyte's Radeon HD 7970 Super Overclock. Taking Tahiti over 1100 MHz is simply inefficient. PowerTune doesn’t help in these scenarios either. In fact, it's counterproductive at the highest setting. The feature pushes maximum frame rates higher as minimum frame rates drop, yielding noticeable stuttering.