Says Johan Andersson from DICE. Andersson said creating a Mantle version of the Frostbite 3 engine took them about two months to complete. Mantle support will be added by an update in late December, nearly two months after the game's release. Jorjen Katsman of Nixxes, the firm porting Thief to the PC, added that AMD's API significantly reduces overhead. The Mantle API has just 8 percent overhead whereas DirectX 11 has an overhead of around 40 percent. Katsman says it's not unrealistic to receive 20 percent extra GPU performance in games with Mantle support.
As reported by tech report:
Andersson didn't bring up performance estimates, but other developers who discussed Mantle at APU13 did. Jorjen Katsman of Nixxes, the firm porting Thief to the PC, mentioned a reduction in API overhead from 40% with DirectX 11 to around 8% with Mantle. He added that it's "not unrealistic that you'd get 20% additional GPU performance" with Mantle.
But the "pink elephant in the room," as he called it, is multi-vendor support. Andersson made it clear that, while it only supports GCN-based GPUs right now, Mantle provides enough abstraction to support other hardware—i.e. future AMD GPUs and competing offerings. In fact, Andersson said that most Mantle functionality can work on most modern GPUs out today. I presume he meant Nvidia ones, though Nvidia's name wasn't explicitly mentioned. In any event, he repeated multiple times that he'd like to see Mantle become a cross-vendor API supported on "all modern GPUs."
I've gleaned more details about Mantle, and I'll share those with you guys when I'm not scurrying between keynotes and meeting rooms. The sense I get from the developers AMD invited to APU13, though, is that Mantle yields considerable benefits in terms of development flexibility and performance, and it's worth implementing even in its current, vendor-locked state. Andersson wasn't the only developer to express a desire for multi-vendor support.
There's no telling yet whether Mantle will ever become a cross-vendor, cross-platform standard, or whether the future holds something different, such as a competing Nvidia API or a future version of DirectX with some of the same perks. One thing is clear, though: Mantle looks set to shake up the industry in a very real way.