GTX 660 SLI vs. GTX 680 vs. HD 7970 GHz – Value & Performance Evaluation
Benchmarks & Conclusion
Here are our results of twenty-eight benchmarks – twenty-five games and three synthetics – compared between the GTX 660 SLI and HD 7970 at GHz edition speeds and versus a stock GTX 680.
We note that in every single case except one, the GTX 660 SLI is faster than either the HD 7970 GHz edition or the GTX 680!
Conclusion
This has been quite an enjoyable hands on experience with these video cards evaluating midrange GTX 660 SLI versus the GTX 680 and versus the HD 7970 GHz editon. We have generally observed very good multi-GPU scaling so that the GTX 660 SLI was able to beat both of our single fastest cards in almost every single situation that we tested. In only one game (Borderlands 2), does a single GTX 680 come very close to GTX 660 SLI performance and in one other game (Sleeping Dogs), the Radeon splits the win with GTX 660 SLI. It appears that the 192-bit bus is no disadvantage for the GTX 660 SLI at even 2560×1600 with maxed-details and AA.
Micro Stutter and Greater than 100% Scaling
Micro stutter bothers some gamers so much so that they cannot ignore it and they return to using a single powerful card while others never notice it at all and will swear that it does not exist. Micro stutter does exist as it is inherent to Alternate Frame Rendering (AFR), but drivers minimize its effects so that generally the performance gained by the second card outweighs any disadvantages.
In the past we noted that in many situations where micro stuttering is evident, the CPU or Graphics are straining and often it may be minimized somewhat by lowering settings. Currently, the “metering” that Nvidia uses in their drivers really minimizes microstutter and the only game that we really noticed micro stuttering, was in Borderlands 2 – especially in the latest DLC. If you would like to weigh on our future testing methods or to specifically discuss micro stutter testing methods, feel free to comment below, ask questions, make requests, or have a detailed discussion in our ABT forum.
We have also occasionally noted CrossFire and SLI scaling greater than 100% in the past. We only see it once in this set of benchmarks (in F1 2010). Sometimes this can be attributed to “benchmark noise”, the way averages are rounded off, or the nature of Alternate Frame Rendering (AFR) where multi-GPU scaling may be slightly better than 100% due to the frames that are read ahead by the CPU.
If frames for a multi-GPU system are only pre-rendered as for a single card there would be less than optimal scaling. The AFR dual-GPU system likely has to render ahead further than a single-GPU system does because there are now two GPUs to feed. In this scenario, the framerate may possibly have higher than 100% scaling during some GPU-bound situations.
In other words, a GPU can render only one frame at a time. If there were no pre-rendering at all, the CPU has to wait before constructing a new frame, while pre-rendering allows the CPU to keep on preparing frames while the GPU is busy. Since the prepared frames are stored in an offline buffer, the GPU ideally never has to wait for the CPU to construct them. Now since the pre-render value is likely higher for a multi-GPU system than it is for a single GPU system, it is possible to achieve greater than 100% scaling. The multi-GPU system’s higher pre-render values makes it probable that the CPU can continue working on frames instead of stopping for a single video card with a lower pre-render value. Of course, this would cause more input lag but that is beyond the scope of this discussion.
Other factors can also contribute to greater than 100% scaling which include “benchmarking noise” – the margin of error built into benching is generally accepted as 1-3% – and also driver bugs that might hold back a single GPU but which don’t show up in multi-GPU situations. Usually you will not encounter this; ideally scaling approaches 100% if your SLI or CrossFire drivers are working perfectly.
In this one case with F1 2010, however, it appears that a driver bug may be causing a single GTX 660 t0 choke at one point, dropping its averages.
Bang for Buck
The top card has never been about bang-for-buck value. This is something that two midrange cards in a multi-GPU configuration can give right now at the possible expense of potential micro stutter, more noise from two cards, and possible future lower resale value. These considerations are something that every gamer needs to weigh. However, the results speak for themselves and GTX 660 SLI proves to give great performance for the gamer’s $440.
Stay tuned, there is a lot coming from us at ABT including a evaluation of the brand new Sapphire Vapor-X CPU cooler! Don’t miss it tomorrow. Stay tuned to ABT for the latest regular news and Top Apps, as well as a Genius PC speaker evaluation all in the coming week.
Happy gaming!
Please join us in our Forums
Become a Fan on Facebook
Follow us on Twitter
For the latest updates from ABT, please join our RSS News Feed
Join our Distributed Computing teams
- Folding@Home – Team AlienBabelTech – 164304
- SETI@Home – Team AlienBabelTech – 138705
- World Community Grid – Team AlienBabelTech
