AMD has issued a statement regarding purported issues with excessive power draw across the PCIe bus, resultant of a single, limiting 6-pin power header from the PSU. We are researching this issue independently and allocating resources to new power testing equipment. We also just purchased a retail RX 480 Reference card, which we will use to determine if the issue occurs on non-review products. So far, it seems to be the case.
Our RX 480 Hybrid mod, which utilized a liquid cooler rather than reference cooler, found that the RX 480 will draw upwards of 192W GPU power, as validated by software. The additional board components are rated for 40W pre-OC, so our overclocked card was likely drawing towards 250W. In such an instance, the GPU will overdraw power through the motherboard, which is potentially harmful to 24-pin headers (rated at 300-350W), the PCIe slot, and board power components. Our motherboard is capable of handling this extra power because we've taken measures to improve delivery, mainly by tapping into PSU power with an EVGA Boost cable and using an additional 6-pin board header for the PCIe bus.
On setups without these precautions, there may be an issue.
Regardless, AMD just issued a statement on the RX 480 and its overdraw:
“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).”
It's worth pointing out that AMD's 8Gbps memory speed is not, in fact, “unprecedented” – but that's nitpicking. Sort of. The bit that matters is that AMD's releasing a driver update that aims to resolve power issues. Short of a hardware change, it is likely that the update will throttle cards as power draw increases. This is something we demonstrate in our upcoming RX 480 Overclocking Tutorial (publication within 24 hours of this post), where a 100% power will throttle clock-rates heavily in some instances.
We will be re-testing the RX 480 with this driver update to determine if performance is down-classed as a result of potential power throttles. If the clock is eaten into to mitigate power draw, framerate will be impacted.
We will use a retail card for additional assurance that it is what the consumer sees, and have purchased one for the test.
- Steve “Lelldorianx” Burke.