Microsoft has been working hard on DirectX 11, which debuted in the Windows 7 Release Candidate. It isn't a brand-new graphics API such as DirectX 10 was; rather than building from the ground-up, Microsoft has refined and improved the last-generation software to try to ensure next-generation performance.
While this probably won't see frame rates jump overnight, several new features mean that the new API should be more scalable and efficient than the older software. Microsoft has concentrated on three broad areas for improvement with the new release: tessellation, multithreaded rendering and shaders.
Tessellation was first introduced in the Xbox 360's Xenos GPU, and reduces the number of polygons used to render objects in the distance and then increasing the detail close up - in other words, using the same number of polygons to achieve more efficient results.
Multithreaded rendering is another area where Microsoft hopes to make the GPU more efficient. Much as desktop applications - including Photoshop CS4 - can take advantage of the multiple cores of a modern CPU, DirectX 11 enables graphical tasks to be handled by multiple processor cores too.
The third main boost has been given to the much-vaunted area of GPGPU (general-purpose GPU). Rather than having hundreds of shaders simply dedicated to graphics - the ATI Radeon HD 4870 has 800, for instance - DirectX 11 enables them to be used in other applications, such as the popular Folding@home research application.
These enhancements and any others planned for DirectX 11 are mere pipe dreams at present, though, because Nvidia and ATI's current-generation GPUs support only DirectX 10, although DirectX 11 cards are on the way.
The current lack of support for next-generation features means that gaming performance between Windows 7 and its predecessors is relatively similar. To test, we used the same rig as with our 2D benchmarks - albeit with a Radeon HD 4890 card rather than an HD 4550 - with Crysis and Call of Juarez, two of the stiffest tests for a modern graphics card.
Windows XP was the fastest system in Crysis, managing 53fps in our high-quality benchmark compared to 48fps from both Vista and Windows 7. But XP's lack of DirectX 10 support means that, even if its frame rates are quicker than its rivals, games just won't look their best on the ageing OS - Call of Juarez, for instance, won't even run without DirectX 10 support.
However, there was little to choose between Windows Vista and 7 when it came to gaming performance. They achieved identical scores of 48fps and 29fps in our high-quality and very-high quality Crysis benchmarks.
And there was little between them in the Call of Juarez DirectX 10 benchmark: while Windows 7 was faster at low resolutions, running at 151fps in the low-quality test to Vista's 138fps, both operating systems scored similarly in more detailed tests, with Vista managing 47fps in the high-quality benchmark and Windows 7 running a frame slower.
Microsoft's decision to use the same core OS as Vista means that incompatible games seem to be few and far between. In short, gamers have nothing to lose from a Windows 7 upgrade - and potentially plenty to gain when support for DirectX 11 arrives.
Also in our series, Windows 7 the complete guide:
Part 6: Blu-Ray and displays
Part 5: The new XP mode
Part 4: Playing DivX and XviD files
Part 3: Will your PC actually boot any quicker?
Part 2: Raw performance benchmarks
Part 1: Good news for gamers?
Also see: The 30 Best Features of Windows 7