Dual-GPU Battle: Does Frame Pacing In Catalyst 13.8 Turn The Tide?

Test System And Benchmarks

The Radeon HD 7990 was officially launched four months ago. So, it's been tough to find extra cards kicking around. But XFX came through for us with its R7990 Triple Dissipation card.

Like most 7990s, it's based on AMD's reference design with a 950 MHz base core clock that stretches to 1 GHz when the thermal headroom allows. It also comes with 6 GB (3 GB per GPU) of 1500 MHz GDDR5 memory. XFX bundles a CrossFire bridge, an HDMI-to-DVI adapter, and a DVI-to-mini-DisplayPort adapter. Aside from the hardware, you get the requisite warranty, installation, and promotional documents, plus a driver CD. Pop the included "Do not Disturb" sign on your door when you want to spend some quality time with your gaming PC.

More important, the R7990 comes with AMD's Never Settle game bundle voucher, good for: BioShock Infinite, Tomb Raider, Crysis 3, Hitman: Absolution, Sleeping Dogs, Far Cry 3: Blood Dragon, Far Cry 3, and Deus Ex: Human Revolution.

We all know that the Radeon HD 7990 requires a substantial amount of power, so XFX also sent its PRO850W 80 PLUS Bronze-certified power supply. This modular PSU employs a single +12 V rail rated for 70 A. XFX claims that this unit provides 850 W of continuous power (not peak) at 50 degrees Celsius (notably higher than the inside of most enclosures).

We've almost exclusively eliminated mechanical disks in the lab, preferring solid-state storage for eliminating I/O-related bottlenecks. Samsung sent all of our labs 256 GB 840 Pros, so we standardize on these exceptional SSDs.

As far as testing goes, we're using FCAT to report frame rates, removing dropped and runt frames from the equation.

We're including side-by-side comparisons from the lossless videos used to create our FCAT-based frame rate and frame time variance data. The results are encoded at half-speed. So, at the YouTube "normal" speed setting (30 FPS), you can scrutinize the result at slower-than-real-time and get a great sense of the differences. Then, if you want to see the output as it appears when we're testing, set the speed to 2x (60 FPS).

The 2x speed option can be accessed via YouTube's HTML5 trial. Enable this feature by going here and clicking the "Join HTML5 Trial" button. Once you're in, close and relaunch your Web browser. You should now have access to HTML5-based speed controls through the settings button on the bottom-right of the video playback window:

A few suggestions about the HTML5 trial. Make sure that the video loads completely before playing it back at 2x. The sped-up content requires more bandwidth, and you don't want hiccups in the stream affecting your perception of the capture. Also, we've seen cases where YouTube doesn't register a speed setting change until the page is reloaded. We recommend watching the video at normal speed before doubling it up. It's much easier to see differences in frame rate smoothness this way. Finally, the YouTube HTML5 trial may demonstrate choppy performance in Firefox, but the experience in IE seems much smoother.

Last but not least, we want to send some props to Chris at Memory Express in Winnipeg, Manitoba for helping us sort out an issue with our display hardware. This isn't the first time these folks have come through for us with some last-minute assistance, so thanks guys!