The Intel Iris Graphics 6100 (GT3) is an integrated Broadwell GPU revealed in Q1 2015.  The Broadwell-GT3 silicon, Iris 6100 will get 48 execution units, a 300 to 1100 MHz dynamic GPU core frequency, and an L4 eDRAM cache. 

Broadwell features a GPU based on the Intel Gen8 architecture, which has been optimized in various aspects compared to the previous Gen7.5 (Haswell). Inter alia, the shader arrays called "subslice" have been reorganized and now offer 8 Execution Units (EUs) each. Three subslices form a "slice" for a total of 24 EUs. Combined with other improvements such as larger L1 caches and an optimized frontend, the integrated GPU has become faster and more efficient than its predecessor.

The Iris Graphics 6100 represents the top-end version of the Broadwell GPU family and consists of two slices with 48 EUs. Beyond that, there is also a low-end (GT1, 12 EUs), a mid-range (GT2, 24 EUs) and a high-end variant (GT3e, 48 EUs + eDRAM), as NoteBookCheck reports:

All Broadwell GPUs support OpenCL 2.0 and DirectX 11.2. The video engine can now decode H.265 using both fixed function hardware as well as available GPU shaders. Up to three displays can be connected via DP 1.2/eDP 1.3 (max. 3840 x 2160 @ 60 Hz) or HDMI 1.4a (max. 3840 x 2160 @ 24 Hz). HDMI 2.0, however, is not supported.

Depending on the specific CPU, the maximum GPU frequency varies between 1000 and 1100 MHz. Even though the Iris Graphics 6100 is technically identical to the HD Graphics 6000, the higher TDP (28 W instead of 15 W) leads to a better utilization of the Turbo Boost and therefore a superior performance. Overall, the Iris 6100 should be slightly faster than a dedicated GeForce 820M.

Nevertheless, games as of 2014/2015 will usually run fluently only at low settings. Utilizing a new 14 nm process, the Broadwell LV chips are specified at 28 W TDP and therefore suited for medium-sized ultrabooks. The TDP is flexible and can be further reduced (23 W), which has a significant impact on performance.