AMD RX Vega 64: The Tom's Hardware Liquid Cooled Edition

Introduction & Test System

Believe it or not, all-in-one liquid coolers can keep more than 400W of waste heat in check, so long as you have the right radiator. How do you generate that much heat in the first place? Buy a Radeon RX Vega 64 and overclock it, of course! Perhaps because Tom's Hardware is a little more discerning with awards than most publications, AMD didn't send over one of its liquid-cooled cards for review. Instead, we set out to build something better than what AMD sells at a hefty premium.

A true custom loop with a full copper block would be a big step up in thermal performance, of course. But not everyone already owns a water-cooling kit, and many gamers are intimidated by the idea of piping together their own pump, radiator, fan, and tubing.

So, we turned to an all-in-one liquid-cooling prototype that, as luck would have it, we had sitting around anyway. Our Alphacool Eiswolf GPX-Pro came with the necessary radiator, tubing, and quick-release fittings. We'll compare the turnkey kit's performance to our own open-loop setup. As we'll soon see, however, there are some good reasons to suggest we could have saved ourselves the trouble.

For our tests, we're starting with a 120mm radiator (the same size AMD includes with its $700 card). AMD's all-in-one cooler costs $80, which is the price the company's partners have to pay for it. It accommodates one (push) or two (push/pull) fans. But we'll show you why a 240mm radiator is the minimum to consider if you plan on overclocking.

First things first, though. We have to provide some necessary context for our results:

We use The Witcher 3 at Ultra HD for our benchmarks because it produces the highest loads and provides a realistic scenario at the same time. As we’ll see later, your workload has a big impact on the clock rates that can be achieved. Also, The Witcher 3 is an ideal stability test for both the GPU and HBM2.Note also that AMD’s drivers reported frequency numbers that were way too high in some cases, until AMD fixed this right before launch. Nevertheless, the inflated numbers made their way into some reviews. So, if you think that our results look suspiciously low, please keep this in mind. Here’s AMD’s statement about the issue:"This new driver also reports the previously advertised GPU boost clock instead of the top DPM peak frequency...We’ve not yet had time to test this functionality with all other aspects of the driver and needs further testing before prime time, but we wanted to enable you to play around with OC!"

Installation & Notes

Don't be bothered by the fact that the thermal paste isn't cleaned up completely. This doesn’t actually make a difference, so long as you're using non-conductive paste. After switching out the cooler more than 10 times, a thorough cleaning job just isn’t possible anymore without endangering the package. In spite of the molding, there’s still some room between the interposer and package substrate. This is why we really don’t want to apply any pressure to the tiny board during cleaning. We only have the one card, after all.

When it comes to picking a thermal paste, stay away from the more viscous options out there. You still want something of high quality, though. Blobs and lines won't work due to Vega’s two HBM modules. Apply a thin and even layer with the help of a spatula instead. We used Kryonaut by Thermal Grizzly, but there are certainly other low-viscosity pastes that work just as well. (See our roundup of 85 thermal pastes for more.

It’s also important to cover the very short voltage converter tops with thermal pads of suitable thickness. Apply them on a larger scale in order to catch some of the board’s waste heat, if you can. And the coils should be included too, if possible, since the voltage converters alone yield a rather small surface area.

Alphacool supplies an active backplate, which is to say that the backplate helps with cooling. It’s not enough to simply cover the parts of the board below the voltage converters with thermal pads. The phase doublers also beg for some cooling attention when they hit more than 110°C in the face of aggressive overclocking. That's why we cut soft pads into large strips to make contact with the backplate in more places than Alphacool originally envisioned.

Conversely, feel free to leave that pad right below the GPU off; if anything, our upcoming infrared measurements suggest it's counterproductive.

The install wraps up with screwing the backplate on (don't over-tighten!). Even if you've never swapped out the cooler on your graphics card before, this shouldn't take more than an hour.

Thanks to Alphacool's quick-release fittings, we’re able to swap between cooling solutions without changing tubing or refilling the loop.

Test System & Methodology

We introduced our new test system and methodology in How We Test Graphics Cards. If you'd like more detail about our general approach, check that piece out.

The hardware used in our lab includes:

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