Maximum PC

AMD RX 7900 XTX Vapor Chamber Woes


- Jarred Walton Jarred Walton has been a PC and gaming enthusiast for over 30 years.

Nvidia was in the hot seat due to the melting 16-pin adapters on its RTX 4090 graphics cards. An investigat­ion determined that the root cause was users failing to fully insert the plug into the receptacle. With a bit of wiggling, the connection could come loose and start arcing, causing the plastic around the socket to melt. As you can imagine, AMD was pleased with its decision not to use the 16-pin connector on its cards.

Several prominent people at AMD mocked Nvidia’s snafu, with one proclaimin­g “We’re going to kick Nvidia’s ass!” Another tweeted an image of the dual 8-pin connectors on AMD’s RX 7900 card with the text, “Stay safe this holiday season.”

Egg, meet face. AMD has had to acknowledg­e that batches of its reference RX 7900 XTX cards have an even bigger problem: they are overheatin­g, throttling, and underperfo­rming. AMD has vowed to replace the faulty cards but, by all accounts, the problem with the reference XTX cards is more widespread than Nvidia’s melting adapter.

AMD’s full statement reads: “We are working to determine the root cause of the unexpected throttling experience­d by some while using the AMD Radeon RX 7900 XTX graphics cards made by AMD. Based on our observatio­ns, we believe the issue relates to the thermal solution used in the AMD reference design and appears to be present in a limited number of cards sold. We are committed to solving this issue for impacted cards.”

Further details implicate the XTX vapor chamber. Vapor chambers are basically a higherperf­ormance take on heatpipes. You have a large chamber with a bit of liquid inside, and the heat from a GPU causes the liquid to evaporate. That phase change helps to wick away a large amount of energy, and then the vapor spreads through the chamber and condenses on the cooling side that’s attached to the radiator fins. With AMD’s RX 7900 XTX, there’s a fine-grained wire mesh on both the top and bottom surfaces to help with the process.

The amount of liquid and the pressure inside the chamber are key factors that need to be carefully controlled. Too much or too little of either and the evaporatio­n and condensati­on process won’t function properly. However, around four to six batches of the cooler didn’t have sufficient liquid placed within the chamber. The result is that the cooling capacity is greatly reduced.

In the case of the RX 7900 XTX, affected cards can quickly reach hotspot temperatur­es of 110°C, at which point they begin to throttle. Depending on how bad the problem is, users might lose anything from a few percent to as much as 10 percent in performanc­e, but that’s only part of the problem. The 110°C hotspot also causes the fan speeds to ramp up by as much as 1000rpm, leading to a much noisier system, and long-term failure.

So, AMD is doing the right thing and replacing the affected cards, but compared to the roughly 50 cases of melting 16-pin adapters Nvidia was dealing with, AMD is

The 7900 XTX’s cooling system features a vapor chamber but, unfortunat­ely, some batches of reference cards had a flaw here.

potentiall­y looking at replacing the coolers on thousands of cards—5,000 seems to be a reasonable estimate. That’s a few orders of magnitude worse than Nvidia’s mistake.

So, how can you tell if you have one of the affected cards? First, it’s only the 7900 XTX ‘Made by AMD’ reference cards that are affected. If you have a 7900 XT or a custom design 7900 XTX, you’re in the clear. Beyond that, AMD says to monitor card temperatur­es while gaming, and in particular the GPU hotspot temperatur­e, to see if it’s hitting 110°C—we’d suggest using FurMark with the GPU oriented in a horizontal position as a quick check. If that happens, you likely have an affected card.

In more bad news, AMD had run out of replacemen­t cards at the time of writing, meaning it could be a few weeks before more replacemen­ts become available— hopefully by the time you read this.

It is a few orders of magnitude worse than Nvidia’s mistake with melting 16-pin adapters.

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