Re:AMD’s aggressive pricing update on the EPYC 7371
by BeeOnRope on Friday December 07, 2018 @08:28PM
(#18633257)
I just ran some tests on CNL and indeed the behavior is very different than earlier chips. I am seeing ~15 cycle divs with no pipelining (i.e,. the latency and inverse throughput are both 15), versus 36+ cycles latency and 25+ cycles inv throughput on Skylake.
Interesting. I found only a few other changes beyond that, so far.
Yes and no. Apparently, my mind messed up my memory. So it was a leaked post on /r/intel. I thought it was for 9000-series, but apparently it was a leak for Cannon-Lake. So I was mistaken.
Second: the post has since been deleted. You can see the claims in the comments still however.
https://old.reddit.com/r/intel/comments/9ol9is/instruction_t...
> FWIW, even for Skylake, Agner reports 26 cycles for a 32-bit idiv, so the chip is already close (if you were talking 32-bit division).
The post used to alleged 20ish cycles for 64-bit division (!!). So I guess that's something to look forward to testing.