Benchmark Results: Overclocking
Over and over, I saw it argued in the comments that the only fair way to compare a GeForce GTX 680 to a Radeon HD 7970 is with both cards overclocked. Because the 680 employs GPU Boost, it purportedly already demonstrates performance close to its limit, whereas Tahiti-based GPUs are known to offer quite a bit of headroom.
And so we went back to tweak our boards more purposefully.
We started with the Radeon HD 7970—a retail board purchased from Newegg—and Catalyst 12.2. It wasn’t difficult at all to max out Overdrive, hitting a 1125 MHz core and 1575 MHz memory frequencies. Attempts to hack CCC and the latest version of MSI’s Afterburner software using well-known registry and config file adjustments proved unsuccessful. Besides, we weren’t looking to disable any of the board’s functionality in order to hit higher clocks anyway. So we stuck to the highest settings enabled by AMD.
The GeForce card actually managed to achieve fairly similar increases. EVGA’s GTX 680 proved stable with its power target at 132% and a 150 MHz core clock offset. The memory clock was far less flexible. We managed a +25 MHz offset, but performance dropped. So, testing was completed at the stock 1502 MHz setting.
The Radeon HD 7970 picks up a ton of speed in 3DMark 11. Although we give the GeForce GTX 680 a higher power target and substantial frequency offset, it doesn’t derive any benefit in this synthetic metric.
Nvidia’s GeForce GTX 680 again fails to realize much of a gain in the face of our offset-based overclock. Meanwhile, AMD’s Radeon HD 7970 enjoys a sizable boost. As a result, our placing for these two products flips, as AMD comes out on top.
Crysis 2, one of Nvidia's TWIMTBP games, is a bastion for the company in the face of poorer showings in 3DMark and Battlefield 3. Although the Radeon HD 7970 sees a roughly 6 FPS average speed-up when we max out Overdrive, that’s not enough to overcome AMD’s deficit to Nvidia playing under DirectX 11.
A 200 MHz overclock propels the Radeon HD 7970 a full 10 FPS faster in DiRT 3. That isn’t enough to catch the GeForce GTX 680, though, which only gains 4 FPS, but started with a larger lead.
Although it again benefits more from overclocking than Nvidia’s GeForce GTX 680, AMD’s Radeon HD 7970 just isn’t as fast in the 64-bit World of Warcraft client.
The Radeon HD 7970 was already faster than Nvidia’s GeForce GTX 680 with 4x MSAA applied to Metro 2033. That lead is maintained when both cards get overclocked.
Overall, it’s pretty easy to see that AMD’s Radeon HD 7970 has more to gain from an aggressive overclock than Nvidia’s GeForce GTX 680. It’s a little disappointing, then, that the Catalyst Control Center driver tops out at 1125/1575 MHz. We started down the road of disabling Ultra-Low Power States and registry hacks to get at more speed, but quickly decided that circumventing beneficial aspects of the hardware was a step too far. Perhaps the company will consider enabling additional scalability in its driver moving forward.
The other conclusion to fairly easily draw is that Nvidia’s GeForce GTX 680 sees much of its headroom exposed by GPU Boost already, leaving less on the table for overclocking. That’ll make it all the more interesting to see what vendors like EVGA do with their modified boards. Using more aggressive air cooling or an integrated water block is almost certainly the key to a more harmonious relationship between GPU Boost and higher clock offsets.