After the AMD Radeon RX 480 was officially launched, several websites reported that their cards were drawing substantially more power from the PCI Express bus than the 75 W allowed by the PCI Express specifications. AMD has now come up with responses to this developing controversy.
2016-07-06 : Added a new page on the AMD driver solution, and our take on it.
2016-07-09 : Added a new section on the Radeon Software Crimson Edition 16.7.1 driver.
Excessive RX 480 Power Draw
The PCI Express specification allows for up to 66 W of power to be supplied by the 12 V line (12 V x 5.5 A) of the PCI Express bus. However, reviewers who have the necessary equipment to measure the power draw from the PCI Express slot have noted that the Radeon RX 480 draws 78-88 W of power from that 12 V line.
If their measurements are correct, the Radeon RX 480 exceeds the PCI Express power draw specification by a minimum of 18% and up to 33%. It also means that the Radeon RX 480 is exceeding its thermal design power (TDP) of 150 watts.
The AMD Radeon RX 480 has to be certified to meet the PCI Express specifications to qualify the card as a PCI Express card, for branding and legal purposes. If the Radeon RX 480 does not fulfil its certification requirements, AMD has to fix the issue within 3 months. Failure to do so will result in the Radeon RX 480 being denied the right to be branded and sold as a PCI Express card.
For certain, AMD would certified the Radeon RX 480 to be PCI Express-compliant before the launch. However, independent testing has revealed that the Radeon RX 480 can and do exceed the power draw specifications. Why there is a discrepancy pre- and post-launch is yet unknown.
Initially, Raja Koduri, Senior Vice President and Chief Architect, Radeon Technologies Group, responded on Reddit that :
Great question and I am really glad you asked.
We have extensive testing internally on our PCIE compliance and RX480 passed our testing. However we have received feedback from some of the reviewers on high current observed on PCIE in some cases.
We are looking into these scenarios as we speak and reproduce these scenarios internally. Our engineering team is fully engaged.
Just two days ago, AMD’s Communications Lead, Garrath Johnson, issued an update on their ongoing investigation of the issue :
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).
We will keep you updated on this developing Radeon RX 480 power draw story, so stay tuned!