Improving Our Testing Methods: Frame Latency
As usual we tested each card with Fraps, which lets us record the average frame rate in seconds over a set amount of time. Typically, we run our tests for 60 seconds. Reporting the average fps (frames per second) is how things have been done for... well, forever. It's a fantastic metric in the sense that it's easy to record and easy to understand. But it doesn't tell the whole story, as The Tech Report and others have shown.
To get a fuller picture, it's increasingly apparent that you need to factor in a card's frame latency, which looks at how quickly each frame is delivered. Regardless of how many frames a graphics card produces on average in 60 seconds, if it can't deliver them all at roughly the same speed, you might see more brief jittery points with one GPU over another -- something we've witnessed but didn't fully understand.
Assuming two cards deliver equal average frame rates, the one with lowest stable frame latency is going to offer the smoothest picture, and that's a pretty important detail to consider if you're about to drop a wad of cash. As such, we'll be including this information from now on by measuring how long in milliseconds it takes cards to render each frame individually and then graphing that in a digestible way.
We'll be using the latency-focused 99th percentile metric, which looks at 99% of results recorded within X milliseconds, and the lower that number is, the faster and smoother the performance is overall. By removing 1% of the most extreme results, it's possible to filter anomalies that might have been caused by other components. Again, kudos to The Tech Report and other sites like PC Per for shining a light on this issue.
Test System Specs
- Intel Core i7-3960X Extreme Edition (3.30GHz)
- x4 2GB G.Skill DDR3-1600(CAS 8-8-8-20)
- Asrock X79 Extreme11 (Intel X79)
- OCZ ZX Series (1250W)
- Crucial m4 512GB (SATA 6Gb/s)
- Gigabyte GeForce GTX Titan (6144MB)
- Gigabyte GeForce GTX 680 (2048MB)
- Gigabyte GeForce GTX 670 (2048MB)
- Gainward GeForce GTX 660 Ti (2048MB) SLI
- Gainward GeForce GTX 660 Ti (2048MB)
- HIS Radeon HD 7970 GHz (3072MB)
- HIS Radeon HD 7970 (3072MB)
- HIS Radeon HD 7950 Boost (3072MB) Crossfire
- HIS Radeon HD 7950 Boost (3072MB)
- HIS Radeon HD 7950 (3072MB)
- HIS Radeon HD 7870 (2048MB) Crossfire
- HIS Radeon HD 7870 (2048MB)
- Microsoft Windows 7 Ultimate SP1 64-bit
- Nvidia Forceware 314.14
- AMD Catalyst 13.2 (Beta 7)