Undervolting AMD’s Radeon R9 Fury For Better Efficiency

AMD’s Radeon R9 Fury has been called everything from a hot plate to a space heater. This doesn’t have to be the case, though. We massively improved the card’s efficiency by undervolting it.

Sapphire recently sent us a sample of its Nitro-branded Radeon R9 Fury card, and the timing couldn’t be better. A few weeks ago, AMD opened the door to voltage adjustments on these cards, which prompted us to exploit the feature in a way you probably wouldn’t expect. Our analysis won’t focus on overclocking. After all, the card is already pushing its limits. We’ll instead try to get it to a more sensible place.

Undervolting With MSI Afterburner

MSI’s Afterburner tool, which is still based on Riva Tuner, now allows enthusiasts to adjust the voltage up or down on a number of AMD graphics cards that couldn’t be tweaked previously. How many millivolts can be pared back before the card becomes unstable? How does that impact performance? How much power consumption can we shave off in the process?

What we’re doing is often called undervolting. However, we generally prefer the more exact description, since voltage isn’t actually changed; instead, the firmware is given an offset. This doesn’t result in a fixed voltage adjustment, but rather a modification of how the telemetry regulates the voltage supply.

To this end, we’re comparing our Sapphire Radeon R9 Fury Nitro to MSI’s GTX 980 Gaming 4G. The two graphics cards offer very similar performance. Before we started our experiment, we downloaded and installed the current version of MSI Afterburner, which looks like this:

The first slider is what we’re looking for—it adjusts the voltage offset. Don’t be surprised if the number changes once you enter it. The figure needs to be a multiple of six. This means -100mV isn’t possible so you’re stuck with -96mV (-6mV x 16).

Note: Every GPU is unique. This means that the lowest number at which a processor still functions without errors can be different from one to the next. What’s more, errors don’t always become apparent immediately. All of a graphics card’s features need to be used for a prolonged period of time to determine if the configuration is stable.

Cards made during AMD’s early production cycle are particularly prone to display problems after undervolting. These GPUs were only made into Furies by a somewhat adventurous unlocking process. The newer ones are a lot easier to undervolt. However, even with these, your mileage will vary.

Our review sample managed -96mV stably enough, other than an occasional drop under extreme load. Values from -48mV to -72mV should be possible for any newer GPU. However, older cards, which we tried with the help of forum members, couldn’t achieve the same low numbers. These graphics cards were almost exclusively bought right after the launch, and could have been unlocked.


When we compare the different voltage targets to MSI’s GTX 980 Gaming 4G, for instance, in a Metro: Last Light loop running at 4K, then the value of our endeavor is plain to see. The Sapphire Radeon R9 Fury X Nitro’s power consumption plummets from 279W all the way down to a much more moderate 213W. Of course, that only works when your GPU is willing to cooperate at such a low voltage.

If you’re aggravated and want to see the same gains from Nvidia’s GPU, get ready for disappointment. Lowering the GPU’s voltage just isn’t in the cards because it’s achieved by decreasing the internal power target. Since GPU Boost is a very fragile system, every little drop has a negative impact on clock rate. In turn, this results in a massive performance hit. It’s not something to complain about, per se. Nvidia simply has its mechanism optimally balanced, so there’s practically no room for improvement. Consequently, MSI Afterburner doesn’t even offer the option to lower the voltage. It can only be increased.

 

[SOURCE:-tomshardware]

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