Benchmarks: Rise of the Tomb Raider, Doom
Rise of the Tomb Raider was tested using the high quality preset with anti-aliasing disabled which allowed the HD 5830 to average 23fps though it did dip as low as 6fps. The 6870 was 35% faster with an average of 31fps, the 7850 brought that figure forward another 39% to 43fps, and the jump from the 7850 to the 270X brought a big 49% boost. Given how demanding this game is on VRAM we suspect the 7850 has been crippled due to its 1GB frame buffer.
Another 32% gain is seen when moving from the R9 270X to the R9 380, as the average frame rate climbs to 85fps. From there we hit 126fps with the RX 480, which is a mighty impressive 48% increase.
Note that Doom was tested using the Vulkan API for GPUs that support it. The HD 5830 and 6870 don't support Vulkan and thus were tested with OpenGL. As a result, both bombed out, delivering well below the acceptable minimum frame rate for playable performance.
The HD 7850 on the other hand sailed along nicely with a 63fps average. This, however, didn't stop the R9 380 from producing 40% more performance with a 121fps average. If you thought that was good, then the RX 480 will impress once again, being 48% faster than the R9 380 with a mighty 179fps.