AMD's Radeon RX 480 offers compelling performance for its price, but some reviewers have discovered a potentially troubling behavior from the card's power-delivery subsystem. Controversy arose when Tom's Hardware and PC Perspective discovered that the reference RX 480 is drawing more power than might be considered reasonable from the PCI Express slot's 12V rail.
The fine folks over at PC Perspective are especially insightful on this point. The site notes that the PCI Express specification limits connected boards to drawing no more than 5.5 amps over the 12V connection from the slot itself. The reference version of that card pulls 7A of current from the slot on average, while overclocking increases that current draw to 8.3A.
PC Perspective contacted some internal sources at motherboard manufacturers to determine whether this behavior—especially that of the overclocked card—would be an issue. The site learned that while the traces on the board likely wouldn't be affected, the pins and connectors on lower-cost motherboards might be harmed over time by sustained operation under the highest loads from the overclocked card.
As you know, we continuously tune our GPUs in order to maximize their performance within their given power envelopes and the speed of the memory interface, which in this case is an unprecedented 8Gbps for GDDR5. Recently, we identified select scenarios where the tuning of some RX 480 boards was not optimal. Fortunately, we can adjust the GPU's tuning via software in order to resolve this issue. We are already testing a driver that implements a fix, and we will provide an update to the community on our progress on Tuesday (July 5, 2016).
Since we don't have the kind of in-depth power measurement hardware that PC Perspective does, we can't independently confirm this issue or its effects. The site does note that it hasn't experienced any negative side effects from running a single RX 480 in its test rigs, though, and we didn't note any weirdness in our test systems, either.
Our original conclusion to our RX 480 review was to wait for custom versions of that card to begin shipping because of noise and temperature concerns, and we think that advice is even more relevant now for folks who might be concerned about the RX 480's power draw. PCPer suggests this issue could be avoided entirely with a single eight-pin connector or a pair of six-pin connectors, and we'd expect most custom boards to feature that kind of power-delivery setup. For now, we'll see what Tuesday brings.