If You Like Sapphire's Vapor-X, Stick With The 3 GB Card
Sapphire's Toxic HD 7970 GHz Edition 6 GB is striking both for its exceptional performance and unexpected noise levels. Its 6 GB of very fast GDDR5 memory does help in certain workloads, but it’s barely noticeable normally at resolutions as high as 2560x1440. That's not enough of a differentiator for a graphics card that costs $600+. Really, it'd take a more competitive price tag to get us excited.
Don't get us wrong; the card is really fast. It would have been even better without AMD's GHz Edition changes, though, including PowerTune with Boost. We saw frame rates actually drop when the feature was pushed to its limits.
Lethal Boost does a good job of enforcing higher GPU and memory clock rates. Performance improves, which comes in particularly handy at higher resolutions. But we could do without the frequency modulation that doesn't even really help reduce power consumption. Also, the fan profile is too aggressive, making it loud.
Manual overclocking could have been very promising on this board, thanks to Sapphire's robust VRM, were it not for the card's inability to throttle down at idle with such a setting dialed in. Over time, the card heats up and makes noticeably more noise. It also dissipates close to 50 W doing nothing at all. This isn't Sapphire's fault, though. We caught the behavior in our Radeon HD 7970 GHz Edition launch coverage, caused by AMD's firmware.
As a result, manual overclocking really isn't a good option. The only practical way to use this board is the way Sapphire set it up.
One Toxic HD 7970 GHz Edition card can drive three or four monitors in a multi-display setup. A second board is almost assuredly needed for higher resolutions, making the 6 GB of on-board memory difficult to utilize. Professionals working in oil/gas applications are more likely to need lots of graphics memory, but they're using FirePro or Quadro cards. More purpose-built solutions exist for large video walls, which generally don't require enthusiast-class 3D performance.
All of that makes Sapphire's Toxic HD 7970 GHz Edition an answer in search of a problem. We can’t think of a usage scenario for which we’d recommend it. If you really dig the effort Sapphire put into its Vapor-X cooling solution, we recommend you check out the Vapor-X HD 7970 GHz Edition 3 GB card, and use the difference to take your better half out to a nice dinner.