AMD's Radeon RX 6600 XT launched earlier today and has already found its place on the list of best graphics cards. While the Navi 23-powered graphics card is a solid performer, it's also quite efficient at Ethereum mining — especially once you optimize your GPU for Ethereum mining.
Clock speeds for the Radeon RX 6600 XT vary from one model to the other, depending on the manufacturer. However, the graphics cards should perform more or less the same before and after optimization. Out of the box, our ASRock RX 6600 XT Phantom Gaming OC pumped out 28 MH/s in Ethash while using 120W of power. That's not that great, but with a bit of tuning — overclocking the GDDR6 memory and limiting the GPU core clocks — we got the hash rate up to 32 MH/s and cut power requirements quite a bit.
If we just concentrate solely on the hash rate, the Radeon RX 6600 XT doesn't look very impressive at all, considering we can squeeze out similar mining performance on a Radeon RX 570 or RX 580 with some fine-tuning. However, the Polaris-based graphics card does draw more power, and that's the area where the Radeon RX 6600 XT really excels. While the Radeon RX 570 or RX 580 can pull over 130W, the Radeon RX 6600 XT kept its power consumption within the 75W range.
The ASRock RX 6600 XT Phantom Gaming OC we used for these tests averaged between 74W and 75W as you can see from our Powenetics equipment, which gives real-time power data. (Look at the bottom-left window, in the bottom-left box where it shows current power draw.) Software-based tools, such as HWiNFO64 or MSI Afterburner typically underreport power consumption. The first exhibited at least 12W to 14W lower values, while the latter's measurements varied by around 15W.
At 32 MH/s, the Radeon RX 6600 XT would sport a performance per watt rating of 0.43. If you look at our list of best mining GPUs, you'll find that the Radeon RX 6600 XT ended up being more efficient than other RDNA2 and Ampere GPUs, such as the Radeon RX 6800 or the GeForce RTX 3060 prior to Nvidia nerfing the Ethereum mining performance of its GeForce RTX 30-series (Ampere) lineup.
The Radeon RX 6600 XT, like any other graphics card launched during the pandemic and global semiconductor shortage, will likely suffer from scalping and limited stock. The Navi 23 graphics card was out of stock at major online retailers, including Newegg and Amazon. Micro Center, on the other hand, had around 2,000 units spread across 25 different locations around the country. That's helpful for those near a Micro Center, and miners will have a difficult time buying sufficient quantities of GPUs through Micro Center, but 2,000 GPUs across the U.S. won't go very far.
Of course, we still need to see how the availability and pricing changes over time. Getting a few thousand GPUs into gamers' hands at launch is a good start, but will AMD and its partners continue to ship thousands of GPUs per week to Micro Center, or will supply slow down to a trickle? If the latter happens, we expect prices will also start to climb.
