Hot Chips ’16: AMD publishes Zen x86 core details

Hot Chips 2016 just finished and one of the interesting parts was the AMD publication focused on their new x86 “Zen” core.

AMD claims Zen will have 40% IPC improvements over Excavator – an impressive achievement, but not guaranteed to beat Intel’s Atom. Zen is also supposed to follow a similar philosophy that Atom does today: the power is kept rather constant across generations while performance increases. That is something AMD refers to as “constant energy per cycle”.

In terms of concrete architectural changes, improvements were made across the board (see figure), with slightly more focus on FPU latency and bandwidth. It would seem reasonable to feed vectorization units, however we still need to seem some performance numbers. The Zen is compliant with major floating point extensions used today, such as AVX1 and AVX2.

Finally, “Zen” features round-robin SMT, and AMD is clearer than Intel on which parts of the CPU are being shared and in what way – see figure below.

AMD SMT usage in Zen

AMD SMT usage in Zen

References: http://www.hotchips.org/