DirectX 12 just sneaked into Windows 10, but you can't use it yet
Don't take my word for it! Install the Windows 10 Preview and run dxdiag.exe, then look for the DirectX Version Info at the bottom of the System tab. Boom! DirectX 12.
But before you get too excited, remember that the mere presence of DX12 in Windows 10 is essentially useless until graphics drivers and other software are released to take advantage of Microsoft's new gaming API. We might not have to wait long for the first of those tools. The day of the big Windows 10 press event, Futuremark told Forbes contributor Jason Evangelho that it hopes to introduce a new "API Overhead Feature Test" to its 3DMark benchmarking suite imminently after this latest Windows 10 Preview build dropped, though Microsoft likely has some sway in the exact release timing.
DirectX 12: Built for gamers, aiming at Mantle
DirectX 12 is one of the key features Microsoft hopes will woo PC gamers--a stronghold of the PC ecosystem, but one largely encamped in Windows 7--towards Windows 10. Microsoft says DirectX 12 will sport a vastly better threading model than the five-year-old DirectX 11, giving developers more console-like "closer to the metal" access to graphics processors. In a nutshell, DirectX 12 can offer much improved performance and (Microsoft claims) up to 50 percent power savings under proper conditions.
If you think it sounds an awful lot like AMD's in-house Mantle technology, well, you'd be right. The two gaming APIs are very similar; check out PCWorld's Mantle versus DirectX 12 overview for more info. In fact, Evangelho reports that the new 3DMark API Overhead Feature Test will test Mantle as well as both DirectX 11 and 12.
Even better, you probably won't need a new graphics card to try out the delicious DirectX 12 goodness whenever it's activated by drivers.
Microsoft has already said it plans to talk more about DirectX 12 at the Game Developers Conference in early March--the same event that Valve plans to reveal more about its Steam Machines!--so I'd expect to see DirectX 12 drivers from Intel, AMD, and Nvidia by then at the very, very latest, especially considering that Microsoft already sneaked DirectX 12 itself into Windows 10.
Until then, there's plenty of fresh stuff in Windows 10 to keep you occupied. I'd suggest checking these 10 killer Windows 10 features out first after signing up for the Technical Preview.