Agner`s CPU blog

Software optimization resources | E-mail subscription to this blog | www.agner.org

RYZEN thoughts?
Author:  Date: 2017-03-16 08:23
It's not clear to me that "compiler shenanigans" are responsible for the difference - which does vary quite markedly between games, and even between different APIs on the same game (eg. DX12 and Vulkan is relatively much worse for Ryzen than DX11 and OpenGL, which is the opposite of what you'd expect from an ordinary CPU bottleneck).

What we do know is that communication between CCXes (each of which carries 4 cores) is somewhat more constrained than communication within a CCX; they are linked by the Infinity Fabric which runs at a speed tied to the memory clock, whereas everything within each CCX runs at core clock speed. Games tend to have a lot of producer and consumer threads which communicate voraciously, and they generally don't achieve full core utilisation on a CPU as highly multithreaded as Ryzen 7, so Windows further complicates matters by migrating threads randomly from one core to another, often *between* CCXes. Productivity benchmarks appear to need relatively little communication between threads, and because all cores are fully utilised, Windows doesn't migrate threads between cores.

Hence productivity benchmarks can use Ryzen efficiently without needing to know about its quirks. Games need to be a bit more intelligent, and some of them apparently have intelligence tuned for Intel CPUs which unfortunately breaks on Ryzen. AMD posted something revealing about F1 2016 recently which illustrates this very neatly.

 
thread Intel's "cripple AMD" function new - Agner Fog - 2009-12-30
reply Intel's new - Felid - 2010-01-01
replythread Intel's "cripple AMD" function new - inhahe - 2010-01-03
last replythread Intel's new - Agner Fog - 2010-01-04
replythread Intel's compiler is the best? new - Weber - 2010-01-04
last reply Intel's compiler is the best? new - Agner Fog - 2010-01-09
reply Intel article new - Agner Fog - 2010-01-22
last replythread Intel's new - Deng - 2016-12-11
last replythread Intel's "cripple AMD" function new - Biplab Raut - 2019-12-20
last reply Intel's cripple AMD function new - Agner - 2019-12-29
replythread Web Parallels new - Jeff Craig - 2010-01-04
last replythread More Parallels new - Agner Fog - 2010-01-23
reply Early Examples new - Yuhong Bao - 2010-02-01
last reply More Parallels new - Yuhong Bao - 2010-02-20
replythread New CPUID manipulation program new - Agner Fog - 2010-01-22
replythread CPUID manipulation through virtualization new - Andrew Lofthouse - 2010-08-16
reply CPUID manipulation through virtualization new - Agner Fog - 2010-08-16
replythread CPUID manipulation program for AMD new - Agner - 2010-10-01
last replythread CPUID manipulation program for AMD new - Ralf - 2012-01-30
last reply CPUID manipulation program for AMD new - Agner - 2012-01-31
last reply CPUID manipulation through virtualization new - akshay - 2015-07-08
last replythread New CPUID manipulation program new - AVK - 2011-02-09
last reply New CPUID manipulation program new - Agner - 2011-02-09
reply AMD Blog on compilers/benchmarch new - margaret lewis - 2010-02-01
replythread New version is still crippling Intel's competitors new - Agner Fog - 2010-06-29
last reply New version is still crippling Intel's competitors new - granyte - 2014-09-16
reply Out of court settlement with FTC new - Agner Fog - 2010-08-05
reply AMD library contains Intel's cripple-AMD function! new - Agner Fog - 2010-08-11
replythread Common math programs are affected new - Agner Fog - 2010-08-20
last reply Preliminary test results for Matlab new - Agner Fog - 2010-09-16
replythread Overview of CPU dispatching in Intel software new - Agner Fog - 2010-08-23
last reply Overview of CPU dispatching in Intel software new - Mingye Wang - 2020-08-31
replythread New Intel compiler version - still the same! new - Agner Fog - 2010-09-22
reply GCC now has support for function dispatch new - Jean-Luc - 2010-09-27
replythread Intel compiler question new - James Russell - 2010-10-11
last reply Intel compiler question new - Agner - 2010-10-12
reply New Intel compiler version - still the same! new - Don Kretsch - 2010-11-29
last replythread New Intel compiler version - still the same! new - Daniel - 2011-12-23
last replythread New Intel compiler version - still the same! new - Agner - 2011-12-25
last replythread New Intel compiler version - still the same! new - Stanley Theamer - 2012-02-12
last reply New Intel compiler version - still the same! new - Stretcho - 2012-03-14
replythread Still no library that is optimal on all processors new - Agner - 2012-04-18
replythread Still no library that is optimal on all processors new - Guest - 2012-05-17
last replythread Still no library that is optimal on all processors new - Agner - 2012-05-17
last replythread Still no library that is optimal on all processors new - David - 2012-05-19
last replythread Still no library that is optimal on all processors new - Agner - 2012-05-20
last reply Still no library that is optimal on all processors new - Bubba_Hotepp - 2012-06-16
last replythread Still no library that is optimal on all processors new - Marat Dukhan - 2013-05-20
last replythread Still no library that is optimal on all processors new - Agner - 2013-05-21
last replythread This is still going on, wow just wow new - Vuurdraak - 2016-11-10
last replythread This is still going on, wow just wow new - Agner - 2016-11-10
last replythread This is still going on, wow just wow new - Vuurdraak - 2016-11-11
last replythread This is still going on, wow just wow new - Denis - 2017-01-02
last replythread This is still going on, wow just wow new - Agner - 2017-01-02
replythread RYZEN thoughts? new - Noob programmer - 2017-03-10
last replythread RYZEN thoughts? - Chromatix - 2017-03-16
last replythread RYZEN thoughts? new - Peter - 2017-04-11
replythread RYZEN thoughts? new - Agner - 2017-04-12
last replythread RYZEN thoughts? new - Ballsystemlord - 2019-02-12
last reply RYZEN thoughts? new - Agner - 2019-02-13
last reply RYZEN thoughts? new - itsmydamnation - 2017-04-21
last reply This is still going on, wow just wow new - Naoki Shibata - 2017-07-19
replythread A long history of legal antitrust battles new - Agner - 2017-07-27
last replythread A long history of legal antitrust battles new - Jorcy Neto - 2017-07-27
last replythread A long history of legal antitrust battles new - Royi - 2018-02-19
last reply A long history of legal antitrust battles new - Agner - 2018-05-15
reply Intel's "cripple AMD" function new - PCPMD - 2019-02-27
replythread Patches and workarounds new - Neville C - 2019-11-21
last reply Patches and workarounds new - Mingye Wang - 2020-09-01
replythread Intel's "cripple AMD" function new - Walker - 2020-06-29
last replythread Intel's "cripple AMD" function new - Forsen - 2020-09-16
reply Intel's new - Agner - 2020-09-16
last replythread Intel's "cripple AMD" function new - ETERNALBLUEbullrun - 2021-11-28
last reply Intel's new - Agner - 2021-11-28
last replythread New Intel compiler. Latest update new - Agner - 2022-08-08
last replythread MKL performance on AMD with the new compiler new - Gil Moses - 2022-08-22
last reply MKL performance on AMD with the new compiler new - Agner - 2022-08-22