When Microsoft announced DirectX 12 yesterday, we learned that a broad swath of existing hardware—including all of Nvidia's DirectX 11 GPUs and all of AMD's GCN-based offerings—would support the new API. That wasn't the whole story, however, as Nvidia's Tony Tamasi clarified in an interview with us today.
DirectX 12 will indeed make lower-level abstraction available (but not mandatory—there will be backward-compatibility with DX11) on existing hardware. However, Tamasi explained that DirectX 12 will introduce a set of new features in addition to the lower-level abstraction, and those features will require new hardware. In his words, Microsoft "only teased" at some of those additions this week, and a "whole bunch more" are coming.
In that respect, the release of DirectX 12 should echo that of previous major DirectX versions: full support for the new API will only be available with a new generation of graphics hardware. That said, the lower-level abstraction seems to be a pretty huge part of what makes DirectX 12 what it is, and many of us will be able to reap the fruits of it on current-gen GPUs. As I outlined yesterday, the lower-level abstraction should translate into performance improvements and CPU overhead reductions.
So far, Microsoft has mentioned only two DX12 features that will need new hardware: new blend modes and something called conservative rasterization, which can apparently help with object culling and hit detection. Neither of those additions sounds hugely groundbreaking, but as Tamasi hinted, they may just be the tip of the iceberg. We'll probably have to wait for another announcement from Microsoft to find out more.