The DirectX 12 API on the other hand will work on Fermi, Kepler and Maxwell and it will enable a radical reduction in submission overhead, as well as better scalability on multicore systems. The goal is a console-like execution environment, a "close to metal" approach that we saw with AMD's Mantle API.
You will need new hardware, next generation hardware to support some of the fixed function features that will become a part of DirectX 12. Nvidia says it will be necessary to “embrace the latest GPU architectural achievements.” In other words future GPUs from Nvidia and AMD will end up having hardware support for the full DirectX 12 feature set and of course these features will be hardware accelerated.
On the other hand the DirectX 12 API will work on Fermi, Kepler and Maxwell. The API is the low level console like access to close to the metal API. We know if might be confusing, as DirectX and DirectX API are two completely separate things that can easily get mixed up.
DirectX 11 API is different from DirectX 11.3, the current revision of the DirectX hardware requirement and this is what actually is making all the confusion. Trough time DirectX 11 evolved to DirectX 11.3, adding some more features to the hardware and many didn’t realize that direct X 11 API has a different path from DirectX 11.3 hardware set.
Maxwell is likely going to get these hardware requirements and be fully compatible with DirectX 12 hardware requirement but from what we know this might mean that faster Maxwell might end up DirectX 12 hardware support while first generation Maxwell GM107 28nm Geforce GTX 750 cards won’t. This is something that we need to wait and see but based on information that we gathered, this is likely to happen.
Pascal 2016 stacked RAM Geforce will end up having full hardware support for DirectX 12 and so will upcoming Maxwell products that we expect later this year.