Power And Efficiency
Despite the marketing behind ZeroCore, and indeed, the technology suite's effectiveness in single- and multi-card configurations, Radeon HD 7970s cannot idle with three monitors attached. The host processor's power use isn't bad, though. This is one of those instances where putting the AMD and Nvidia cards into separate charts make sense, since we're trying to compare CPU-to-GPU pairing, rather then CPUs or GPUs alone.
Regardless of whether you're running under an AMD or Intel processor, adding a second Radeon HD 7970 appears to impart far greater power consumption than a second GeForce GTX 680. Single-GPU load power is comparable between the competing graphics cards.
Those power draw differences are reflected in reduced efficiency. Comparing performance to power, GeForce efficiency appears to increase in SLI, while Radeon efficiency appears to drop in CrossFire. None of this gets us closer to figuring out whether AMD’s fastest CPUs allow Nvidia's graphics hardware to reach further than its own, however.