Intel Gen12 Graphics Bring EU Fusion - EUs Fused In Pairs

While we remain eager to find out more about (and benchmark) Intel Gen12 graphics in Tiger Lake and Xe discrete graphics with this generation bringing the biggest changes to the ISA since i965, Linux patches and bug reports do continue offering new tid-bits of information on Gen12.

One bit that I don't believe has been reported publicly or at least not widely is that starting with Intel Gen12 graphics there is "EU Fusion" or the execution units now being paired for yielding a larger warp size.

A bug report for Mesa this week mentions by one of the Intel open-source developers, "Gen12 EUs are arranged in pairs which execute instructions in lockstep, giving an effective warp size of 64 threads in SIMD32 mode, which seems to increase the likelihood for control flow divergence in some of the affected shaders significantly."

Having a warp size of 64 threads for SIMD32 seems to be causing some unexpected performance/issues within Intel's longstanding open-source driver code albeit the issues are being worked out ahead of launch, hence this newest bug report. In turn going through past Mesa bugs there have been other reports with "EU Fusion" in the context of Gen12.

But that's all for now in terms of new details. As with most hardware launches, when finding Gen12 in Tiger Lake laptops or DG1, you will certainly want to be running the very latest Linux kernel and Mesa for the best possible support. It's looking like in early September is when Intel will reveal more Gen12 / Tiger Lake details.