Doom's Vulkan renderer is a staple of our graphics card reviews and a favorite of AMD tech demos. Let's see if the RX Vegas have made a deal with the devil for the performance lead at maximum settings and a resolution of 2560x1440.
Doom's Vulkan renderer is always a bright spot for Radeons, and the Vega cards don't disappoint out of the gate. The RX Vega 56 outperforms even the GTX 1080, and the RX Vega 64 is 11% faster still in average frame rates. Both Radeons and the GeForce GTX 1080 deliver impeccable 99th-percentile frame times, as well. The GTX 1070's 16.1-ms 99th-percentile result is still good, but in a fast-paced game like Doom, you'll notice the frame-rate drops that lead to such a figure.
Our "time-spent-beyond-X" graphs can be a bit tricky to interpret, so bear with us for just a moment before you go rocketing off to the conclusion. We set a number of crucial thresholds (or bins) in our data-processing tools—50 ms, 33.3 ms, 16.7 ms, 8.3 ms, and 6.94 ms—and determine how long the graphics card spent on frames that took longer than those times to render. Any time over the limit ends up aggregated in the graphs above. Those thresholds correspond to instantaneous frame rates of 20 FPS, 30 FPS, 60 FPS, 120 FPS, and 144 FPS, and "time spent beyond X" means time spent beneath those respective frame rates. We usually talk about these results as a proportion of the one-minute test runs we use to collect our data.
If even a handful of milliseconds make it into our 50-ms bucket, we know that the system is struggling to run a game smoothly, and it's likely that the end user will notice severe roughness in their gameplay experience. Too much time spent on frames that take more than 33.3 ms to render means that a system running with traditional vsync on will start running into equally ugly hitches and stutters. Ideally, we want to see a system spend as little time as possible past 16.7 ms rendering frames, and too much time spent past 8.3 ms or 6.94 ms is starting to become an important consideration for gamers with high-refresh-rate monitors and powerful graphics cards.
With a fast-running game like Doom, it makes the most sense to start our analysis at the 8.3-ms mark. Recall that any time spent past this point means the frame rate will drop below 120 FPS. Here, the RX Vegas prove their mettle. The RX Vega 64 spends just about three-and-a-half seconds of our one-minute test run below 120 FPS, while the RX Vega 56 spends five seconds working on tough frames that similarly dip its instantaneous frame rate. The GTX 1080 delivers a similarly respectable result, but the GTX 1070 spends a whopping one-quarter of our test run working hard.