A DirectX 11 GPU
While the improvements on the CPU side mainly concern implementation details, the changes made to the Ivy Bridge graphics core are much more significant. To recap, the Sandy Bridge family processors used one of two graphics cores, the HD 3000 or HD 2000, both of which were limited to DirectX 10.1. For 2012, Intel is finally giving official DirectX 11 support, which is great news.
In terms of the architecture, the Intel GPU has been broadly designed along the lines of the previous version with a few adaptations. Intel is above all putting the accent on architecture flexibility so that it can be adapted as well as possible to reductions in the number of shader unit blocks (Execution Units). While the HD 2000 and 3000 had six and twelve blocks respectively, the HD 4000 has sixteen EUs and the 2500 six.
DirectX 11 support means that there’s a tessellation unit as well as compute shader support, requiring several changes to be made to the EU blocks: the addition of a local shared memory as well as more flexible memory accesses thanks to scatter/gather operations. Moreover, Intel has optimised the EUs and increased yield by making the most of their processing unit parallelism.
There have also been some other small changes. There’s accelerated processing performance for the Geometry Shaders and the Stream-Out, while the setup part is able to eject the triangles that are out of the field of vision of the camera more rapidly. The texture units have also become more efficient and Intel has announced better quality anisotropic filtering. The last noteworthy architecture change comes with the introduction of a level 3 cache within the IGP so as to limit demands on the LLC. The size of this cache hasn’t been given.
Like SandyBridge, Ivy Bridge also has a block within its IGP dedicated to video compression and decompression. When it comes to video decoding, Intel hasn’t announced any changes and we still have full accelerated decoding of the MPEG2, VC1 and AVC formats.
For encoding, the QuickSync unit is back with full hardware encoding of the AVC format as well as partial MPEG 2 and VC1 encoding. Although MVC (3D version of AVC standard) seems to have featured at IDF, we haven't been able to find any trace of it in the documentation supplied by Intel. Either it isn’t supported or it will be implemented in a forthcoming version of MediaSDK. In effect, to benefit from QuickSync accelerated video encoding, applications developers must use an Intel library (MediaSDK). QuickSync has been announced as being faster though nothing has been said on any improvements to quality. We’ll check all this further on in the test.
Three screens, or almost
Note finally one other change to the display interface (FDI). Intel is now giving us two independent links based on DisplayPort and integrated into the processor itself. They can be partitioned into three independent outs. In theory, then, Ivy Bridge can support three screens. To go with this option however, compatibility with Sandy Bridge processors has to be sacrificed and as we saw in our Z77 motherboard review, none of the models on the market offer the simultaneous three screen option. It should however be available on mobile platforms on condition that two screens use a DP connection (which can be the screen that comes with the machine if it's connected via the eDP standard).