FrontlineJaguar said:
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There is so much nonsense "explained" in this thread that it is difficult to stay on topic, but to give you a rough overview:
Mantle is an attempt at marrying the cpu with the gpu(s) by avoiding cpu draw calls as much as possible. All DirectXs (before 12, and we don't really know what DX12 does better at this time) contain two parts. The first part (made by MS) is visible to the programmers and basically a list of functions you can call to do "graphics stuff". The second part (made by ATI/NVidia) is the actual translation of these functions for the various gpu chips. All these years, communication between these two parts consisted of "cpu draw calls" - basically the cpu tells the gpu what to draw and where to draw it. Since cpu and gpu memory is separate on pcs, this required a lot shoveling around commands and memory. Mantle (on a system with unified memory) greatly reduces those cpu draw calls, avoiding most of this shoveling around memory which makes the graphics system much faster. Maybe. Maybe not. It depends what game you are playing. Games can be cpu limited (there is just too much to calculate into a single frame) or gpu limited (there is just too much to draw for a weak gpu).
If your game is gpu limited, then there is no point in Mantle. In theory, you can draw call much more than without Mantle, but your gpu won't be able to do it so you won't see any difference in the end. If your game is cpu limited, then you will see a drastic increase in performance if you have a strong gpu, since you can now execute more graphic commands. This is what people have seen testing Battlefield 4 with Mantle on the pc. Using Radeon 290Xs, the diffferences can be up to 25%, using weak Radeon 260s, there was nothing to see at all.
Now the big question is what is the XBox One and PS4 apu? Both feature unified ram and (depending who you want to believe) full heterogeneity. We know that the Jaguar cores are not exactly berserkers when it comes to performance, but as of yet no developer has complained about insufficient cpu power. So we can (at this point) conclude that games are not cpu limited on the new consoles. That brings up the the question of how strong the gpus are in the apus. Here we know that the more powerful the gpu, the better the performance. However, neither gpu is even close to a Radeon 290X, but close to a Radeon 260, so judging from pc tests we must conclude that DX12 implemented on the XBox One will show No to insignifant improvements. Assuming that the current driver (which is a variant of DX11) already uses some kind of low-level mechanism. In the unlikely event that this is not the case and they are using run-of-the-mill software drivers, we could see a 5% improvement (then again, we have not discussed the part of the XBox One Supervisor which directly interferes with all this "mantle-like" process).
So in short, don't expect miracles from DX12 (whenever it actually comes out) on the XBox One console. Enjoy reading misterxmedia's blog but don't believe a second there is any substance in those ramblings.
