The ramifications of this is that not only is the total number of EUs increased by 20% from 20 to 24, but Intel has greatly increased the ratio of L1 cache and samplers relative to EUs. There is now 25% more sampling throughput per EU, with a total increase in sampler throughput (at identical clockspeeds) of 50%. By PC GPU standards increases in the ratio of samplers to EUs is very rare, with most designs decreasing that ratio over the years. The fact that Intel is increasing this ratio is a strong sign that Haswell’s balance may have been suboptimal for modern workloads, lacking enough sampler throughput to keep up with its shaders.
Moving on, along with the sub-slices front end and common slice are also receiving their own improvements. The common slice – responsible for housing the ROPs, rasterizer, and a port for the L3 cache – is receiving some microarchitecture improvements to further increase pixel and Z fill rates. Meanwhile the front end’s geometry units are also being beefed up to increase geometry throughput at that end.
Much like overall CPU performance, Intel isn’t talking about overall GPU performance at this time. Between the 20% increase in shading resources and 50% increase in sampling resources Broadwell’s GPU should deliver some strong performance gains, though it seems unlikely that it will be on the order of a full generational gain (e.g. catching up to Haswell GT3). What Intel is doing however is reiterating the benefits of their 14nm process in this case, noting that because 14nm significantly reduces GPU power consumption it will allow for more thermal headroom, which should further improve both burst and sustained GPU performance in TDP-limited scenarios relative to Haswell.
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