Tomb Raider received the bulk of our attention because of its odd behavior. But it too typifies the issues AMD is facing.
Let’s start with the chart above. It’s correct for the in-game benchmark we ran. FCAT says we’re seeing an average of 57 FPS. Fraps confirms that 57 FPS sounds about right. And our previous FCAT-generated chart said 51 FPS. In all cases, that’s negative scaling compared to one Radeon R9 295X2 at 60 FPS.
Now, bear in mind that this is a benchmark taken straight from the game. It was chosen by our very own Paul Henningsen for its load and repeatability compared to sequences elsewhere. If you instead choose to run Tomb Raider’s built-in benchmark, you’ll start with around 56 FPS with one Radeon R9 295X2 and end up around 100 FPS. That’s the result AMD is expecting, and we replicated it on our side.
So we have an in-game benchmark that is helped along by four GPUs and a real sequence from Tomb Raider that scales negatively. Almost certainly, something is bottlenecking AMD’s cards, since we have folks at iBuyPower running numbers concurrently using our test and showing that you can use two, three, and four GeForce GTX Titans and still scale performance.
But why the negative scaling? It also turns out that, with a single Radeon R9 295X2 under the hood, there’s an aspect ratio bug, which renders the scene offset to one side. This means less of Lara is rendered on a more regular basis, lightening the load. Switching to quad-CrossFire fixes the aspect ratio, creating a more demanding benchmark. And thus, the frame rate drops compared to a single card.
The red line speaks for itself; one Radeon R9 295X2 outperforms two, but only because the sequence it’s rendering is also incorrect. There are bugs that need to be fixed.
As two Radeon R9 295X2s struggle with whatever’s going on in Tomb Raider, frame time variance is all over the place in a bad way. As you might have guessed, stuttering is a prominent issue in this game as well, and it’s so much worse with four GPUs than two.
And there’s what it looks like over time. Ouch.