Even the most hard-core Radeon fanboys will admit that the red team's older high-end GPUs consume a lot of power. AMD knows this too, of course. With the Crimson update last year, the company supplied a band-aid for the issue with its Frame Rate Target Control feature. This tool lets users set a target framerate on a global or per-game basis, and the driver will intelligently throttle the GPU to try and keep the game at that framerate.
Radeon Chill, then, is an expansion of that concept. With Chill enabled, the driver monitors user inputs to determine whether quick motion is happening in-game. If not much is going on, the GPU will move to a lower power state, reducing the game's framerate. Once the user is active again, the framerate will increase as the GPU ramps its clock rate back up. All of these transitions happen nearly instantaneously, and with no specific action required of the user. AMD says this dynamic frame-rate control "has the potential to reduce the GPU’s power consumption, heat production, temperatures, and cooling noise without perceptibly altering the gaming experience."
Chill requires AMD to implement support for the feature on a per-game basis, and the company has already done so for 18 games. Currently, all of the supported games use the DirectX 9 and 11 APIs. AMD says it intends to support more games and APIs soon, though. Users can enable or disable Chill globally, and define a hotkey (default F11) to enable or disable the feature manually.
With Chill enabled, minimum and maximum framerates can be set on a per-game basis in Radeon Settings. The default range for all of the supported games that I own seems to be 40-144 FPS, although the upper bound can go as high as 300 FPS.
In our initial look at Chill using AMD's pre-release software, we couldn't get the feature to work quite right. We tested Chill with Counter-Strike: Global Offensive and found that the feature wanted to hold frame rates steady at around 62-64 FPS, on average. You can see that behavior in the graph above—there's little variation in frame times. That's not how Chill was supposed to work.
After my initial look at Chill, TR Editor-in-Chief Jeff Kampman gave the utility a shot with AMD's release version of ReLive and found it worked as expected, so he graphed the frame times from a 40-second run through CS:GO's weapons course with Chill on and Chill off. You can see how Chill rapidly varies frame times in response to intermittent user input when Jeff was standing still while shooting wooden targets with a lot of mouse clicks. You can also see how it holds frame times at about 16.7 ms (or 60 FPS) during periods of constant input, like running between segments in the weapons course. At the end of the run, where Jeff is looking at the course timer while standing still, you can see how frame times climb as Chill limits CS:GO to running at 40 FPS—our configured Chill minimum.
With Chill off, the game ran around 100 FPS on average. As you might expect, Jeff says the game felt more fluid overall with Chill off, but critically, it didn't feel any more responsive. In fact, you can see some spots in the frame-time graph above where our Chilled RX 480 actually seems to put out frames faster in response to user input (especially during frames 700 to 1000 or so) when compared to the run with Chill off. That result does seem to mesh with AMD's claim that Chill can improve responsiveness by keeping more of the GPU available for times when fast rendering in response to user input is needed. Fascinating.
Typically, we'd knock a card for delivering frame times as varied as these, but aside from the expected drop in animation fluidity that comes with a move to 60 FPS from 100 FPS on average, Jeff says the Chilled RX 480 felt perfectly smooth and snappy in use. If you can tolerate a slightly less fluid experience, it might be worth turning on Chill in a game that can typically churn out multiple hundreds of frames per second and seeing how it feels. Heck, your K:D ratio might even improve.
Although he unfortunately didn't have time for formal measurements, Jeff also notes that his RX 480's noise levels dropped from "noticeable" to "inaudible" while he had Chill on. For gamers who are in shared spaces like dorm rooms or offices, Chill could let them game without disturbing others. It could also limit heat output in spaces where air conditioning isn't available. Jeff says his Kill-a-Watt showed about 160W of system power consumption with Chill on, compared to 250-260W with it off. That's significantly less waste heat being dumped into the room, and beefier Radeons might see even larger drops.
Although Chill's dynamic frame-rate control didn't work for me in our first round of testing, I definitely saw similar benefits for heat and noise. My Sapphire Tri-X R9 290X normally sits at a toasty 82° C while gaming, and its triple fans do their best to imitate a leaf blower. After an hour of playing Warframe with Chill enabled, however, the GPU core never went above 72° C, which means the fans on my graphics card never went above 39% of their duty cycle (a speed of around 1800 RPM). At that speed, they're barely audible. It certainly was an unusual change in character for the old Hawaii card, and the 15% reduction in GPU core temperatures I saw even beats AMD's claim of 13% lower GPU temperatures on an RX 480.
Our tests aside, AMD showcased Chill with some results from World of Warcraft in its reviewer's guide, and that game seems quite amenable to Chill's magic. The graph above shows a closer look at how Chill produces "slower" frames at idle and dynamically responds to user input by increasing performance when needed. AMD warns that "the benefits of Radeon Chill will vary depending on the game and on the performance of the system in question, and your experience with Radeon Chill may differ across game titles," though, so your mileage may vary.
Overall, Chill is one of the most handy and fascinating utilities we've used with a graphics card in some time. If you have a Radeon, it's well worth giving Chill a shot and seeing whether you can notice a difference in perceived performance. We hope AMD broadly expands Chill compatibility soon.