The AMD Radeon RX 480 card got released yesterday, and since there are more and more reviews surfacing, there are reports of potential problems with the card’s power consumption. Although RX 480 has an official 150W TDP rating, multiple reviewers reported about the card drawing excessive amounts of power from PCI-Express slot.
Since the card is equipped with one 6-pin connector, the maximum amount of power it uses shouldn’t go over 150W (6-pin connector gives 75W plus 75W coming from PCI-Express slot). But some reviewers, who have access to the power measuring equipment, got different results.
Review published on Golem.de states, “Our measurements show that the reference design easily overloads PCIE slot. To be specific it’s 5.5 amps at 12 volts, 66 watts total. The Radeon RX 480 draws 78-83 watts out of the slot, which is more than power coming from 6-pin connector. Excessive load from PCIe slot is not limited because it’s within safe reserves.”
Below you can see graph showing card’s power consumption in The Witcher 3.
A review published on Tom’s Hardware tells us that “AMD’s Radeon RX 480 draws an average of 164W, which exceeds the company’s target TDP. And it gets worse. The load distribution works out in a way that has the card draw 86W through the motherboard’s PCIe slot. Not only does this exceed the 75W ceiling we typically associate with a 16-lane slot, but that 75W limit covers several rails combined and not just this one interface.”
Further on, it reads, “With peaks of up to 155W, we have to be thankful they’re brief, and not putting the motherboard in any immediate danger. However, the audio subsystems on cheaper platforms will have a hard time dealing with them. This means that the “you can hear what you see” effect will be in full force during load changes; activities like scrolling may very well result in audible artifacts.”
It seems that RX 480 uses way too much power from PCIe slot, and the situation is even worse when overclocking. PCPerspective got some rather grave results when running the new Tomb Raider on OC RX 480, “Ouch! In Rise of the Tomb Raider, the Radeon RX 480 was using about 200 watts of power when overclocked, a 33% increase over stock settings. In The Witcher 3, that number falls to about 180 watts while overclocked, but you can clearly see we are hitting a power limit on the card and it is throttling back.”
Image source: PCPerspective
AMD is aware of this problem, during Reddit AMA session, Raja Koduri got asked about the problem, his response is as follows, “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.”
Robert Hallock, Head of Global Technical Marketing at AMD, further explained that,
“1) The RX 480 has passed PCIe compliance testing with PCI-SIG. This is not just our internal testing. I think that should be made very clear. Obviously, there are a few GPUs exhibiting anomalous behavior, and we’ve been in touch with these reviewers for a few days to better understand their test configurations to see how this could be possible.
2) Update #2 made by the OP is confused. There is a difference between ASIC power, which is what ONLY THE GPU CONSUMES (110W), and total graphics power (TGP), which is what the entire graphics card uses (150W). There has been no change in the spec, so I would ask that incorrect information stops being disseminated as “fact.”
We will have more on this topic soon as we investigate, but it’s worth reminding people that only a very small number of hundreds of RX 480 reviews worldwide encountered this issue. Clearly, that makes it aberrant, rather than the rule, and we’re working to get that number down to zero.”
It seems that a simple 8-pin connector would make this problem completely disappear.