That's quite a huge jump in performance, almost 50% gains!
It's because of AMD's piss poor dx11 driver performance, that's why the difference is so large.
http://www.eurogamer.net/articles/digitalfoundry-2015-why-directx-12-is-a-gamechanger
In the graphics card market, AMD is more competitive - but still faces significant challenges from its implacable rival, Nvidia. Thanks to some well-judged price adjustments and the recent arrival of 300 series graphics hardware, the red team has worthy hardware to compete with most of Nvidia's product line, but what's become increasingly apparent over the last nine months is that AMD's DirectX 11 driver is sub-optimal, particularly relevant for those looking to build a budget PC - an area where AMD offers the best theoretical price/performance level in the market.
We first noticed the issue back in November 2014, when we tested Call of Duty: Advanced Warfare. A Core i3 and i7 run the game in a very similar manner if you have an Nvidia card, but if you're using an AMD GPU, performance collapses whenever the system is drawing a more complex scene. Advanced Warfare isn't a one-off scenario either. Tune your system to favour frame-rate over visual effects and you'll run into a CPU bottleneck on AMD hardware much faster than you will with the Nvidia equivalent. Take a look at this shot of The Crew. The R9 280 is a great piece of hardware and phenomenal value at £130-£140, but pair it with a Core i3 instead of a more capable quad-core processor, and a third of its performance vanishes in draw-intensive areas. Meanwhile, once again, the Nvidia equivalent card holds up effectively.
To cut to the chase - most PC hardware reviews will tell you that the AMD graphics cards aimed at the budget gamer are more capable than the Nvidia equivalents, and in a benchmarking scenario where the GPU is paired with a high-end CPU, that is undoubtedly the case. However, in CPU-limited scenarios, AMD's hardware is let down heavily by the sub-optimal driver, meaning that in many modern games (but we should stress - not all), Nvidia's less capable parts actually hand in more consistent performance. It's for this reason that our budget PC build features an Nvidia GeForce GTX 750 Ti, even though AMD offers a competing product often on sale for just a few pounds more - the R9 270X - which absolutely monsters it in terms of raw benchmarks.
So, what's going on? Well, before your graphics card renders any scene, the CPU needs to simulate the in-game world, then prepare the instructions for the GPU to draw the scene. The more complex the scene, the more 'draw calls' are prepared by the CPU. Frame-rate tanks on Call of Duty in more complex scenes - when there's more stuff to draw - then normal service resumes in less complex areas. It's the same with The Crew: frame-rates are fine outside of city scenes, but once you enter more complex environments, performance suffers. In short, Nvidia's driver is processing the same draw calls much more efficiently than its AMD equivalent, maintaining high frame-rates and leaving more CPU resources open to the actual game logic.
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