DirectX 12 is incoming. Microsoft didn’t name any hardware, but nVidia has said Fermi and newer GPUs will be able to run it, as will all AMD 79xx and newer GPUs. Intel has also said recent GPUs they made will also support DX12. That covers most recent PCs and x86 tablets.
Promised features of DirectX 12 include up to a 50% reduction in power usage and up to a 50% boost in CPU performance compared to DirectX 11.2 along with hardware access to the GPU and CPU by developers, enabling game console level performance. For example, if you tossed Windows 8.1 onto a PS4 or Xbox One, game performance would drop quite a bit due to overhead, but if you put Windows 10 on those devices, which is of course not possible, game performance might actually increase a little compared to the OS which ships on those devices.
Nice, but what about existing phones and ARM tablets? The Lumia 920? No. HTC 8X? Definitely not. In fact, many early Windows Phone 8 devices will be SOL when it comes to DirectX 12 games and apps, unless Microsoft has worked some magic. Why is this? It comes down to the SoC which was implemented in these devices.
The Qualcomm Snapdragon S4 MSM8960 uses an Adreno 225 GPU, which only supports DirectX 9.0c. The Lumia 1020, 928, 925, 920, 810, 820, and 822 all use the Adreno 225 GPU. Newer Lumia phones use a SoC which has Adreno 3xx GPUs on die. The 920T, 2520, 1520, 1320, Icon, and the x3x series (devices which shipped with 8.1) may be able to support the new DirectX version, but these GPUs are restricted to a DirectX 9.3 feature level, which is basically a way to enable some features of DirectX 11.1 on 9.3 class chips. DirectX 12 may also be able to utilize some advanced features of these chips, but without further information I wouldn’t hold my breath.
Indeed, all existing Windows Phone devices, and RT tablets, even those made by Blu and HTC, use either Adreno 3xx or 2xx, which may lead to them either being left out when DirectX 12 games begin to arrive in the Windows Store, or holding back development which utilizes the newer DirectX 12, thus hobbling universal games out of the gate. I don’t think any sane developer would want to exclude such a large, existing pool of devices, nor would they want to take the time to develop two separate versions of their games, one using DirectX 12 and another using DirectX 9.
With all this in mind, be prepared to see a slow implementation of DirectX 12 in games which are “Modern” app as opposed to Win32. On the Win32 side, I’m sure we’ll see games and applications using DirectX 12 and DirectCompute begin to arrive within months of the new OS reaching RTM.