Thief and Arma 3 Results
Thief doesn't suffer from Mantle's high memory requirement in Battlefield 4, showcasing gains with AMD's API across all Radeon cards with a single exception: the Radeon R9 285. AMD's new card actually shows a performance deficit with Mantle enabled. It looks like the new Tonga driver needs some work to accommodate the new product.
As for frame time variance, there is definitely some latency with this engine. It is mostly within acceptable limits with the exception of the GeForce GTX 660, a card that demonstrates significant spikes above 15 milliseconds.
Next up is ARMA 3, a game that slightly favors the Radeon R9 285's architectural improvements and color compression over the Radeon R9 280's brute force approach. It is interesting to see the frame time latency results, with the GeForce cards suffering consistently higher average and 75th percentile numbers, while the Radeon R9 285 and 270X have the highest 95th percentile spikes.