It was not tailored for any specific architecture. It overlaps different rendering passes for asynchronous compute, in paraller when possible. Drivers determine how they process these - multiple paraller queues are filled by the engine.
The reason Maxwell doesn't take a hit is because NVIDIA has explictly disabled async compute in Maxwell drivers. So no matter how much we pile things to the queues, they cannot be set to run asynchronously because the driver says "no, I can't do that". Basically NV driver tells Time Spy to go "async off" for the run on that card. If NVIDIA enables Asynch Compute in the drivers, Time Spy will start using it. Performance gain or loss depends on the hardware & drivers.
Yes it is. But Engine cannot dictate what the hardware has available or not.
Async compute is about utilizing "idle" shader units. Slower the card, less idle ones you have. Less capable hardware may also be hard pressed to utilize all of them even if the engine asks nicely. Also there may be limitations as to what workloads in the engine *can* run in parallel. Yes, Time Spy is very graphics-heavy, since, well, its a graphics benchmark. But even there many of the rendering passes have compute tasks that can use this.
Ultimately some AMD cards gain quite a bit (ie. they have a lot of shader units idling while rendering and they are very good at using them for the available paraller loads). Some AMD cards gain less or not at all (either less capable at paralleriziing, less idle shader units or no idle shader units at all - for example a HD 7970 is hard pressed to have any to "spare")
Some NVIDIA cards cannot do this at all. The driver simply says "hold your horses, we'll do this nicely in order". Some NVIDIA cards can do some of it. They might use another way than AMD (more driver/software based), but the end result is the same - the card hardware is capable of doing more through some intelligent juggling of the work.
