AMD Gives Ryzen Status Update, Dismisses Reports Of Windows 10 Thread Scheduler Conflicts

AMD Ryzen

It has been two weeks since AMD launched its Ryzen processor line in conjunction with its AM4 platform. The feedback has been mostly positive, save for lower-than-expected gaming performance at 1080p. AMD touched on the subject, saying that today's games are not optimized for AMD hardware, and that 1080p gaming performance will improve in time as developers take advantage of Ryzen's architecture and features. Be that as it may, some have surmised the real problem has to do with a conflict between Ryzen and Windows 10 thread scheduling. Is there any merit to that? AMD says no.

"We have investigated reports alleging incorrect thread scheduling on the AMD Ryzen processor. Based on our findings, AMD believes that the Windows 10 thread scheduler is operating properly for 'Zen', and we do not presently believe there is an issue with the scheduler adversely utilizing the logical and physical configurations of the architecture," AMD said.

"As an extension of this investigation, we have also reviewed topology logs generated by the Sysinternals Coreinfo utility. We have determined that an outdated version of the application was responsible for originating the incorrect topology data that has been widely reported in the media. Coreinfo v3.31 (or later) will produce the correct results," AMD continued.

AMD also took a look at the performance difference between running Ryzen in a Windows 7 setup versus a Windows 10 configuration. It did not find any issues with thread scheduling in either setup and determined that any performance differences users might observe can be attributed to software architecture differences between the two OSes.

Ryzen 7 1800X

The Sunnyvale chip designer also reiterated its stance that performance will improve over time. While there are many applications that make good use of Ryzen's efficient architecture, it admits there are others that can do a better job utilizing the topology and capabilities of Ryzen. AMD said this is something that is already being worked on through its Ryzen dev kit program.

In the meantime, AMD confirmed reports that it advises setting the Power Plan in Windows 10 to High Performance for Ryzen to fully shine. There are two reasons why AMD makes this recommendation:
  1. Core Parking OFF: Idle CPU cores are instantaneously available for thread scheduling. In contrast, the Balanced plan aggressively places idle CPU cores into low power states. This can cause additional latency when un-parking cores to accommodate varying loads.
  2. Fast frequency change: The AMD Ryzen processor can alter its voltage and frequency states in the 1ms intervals natively supported by the Zen architecture. In contrast, the Balanced plan may take longer for voltage and frequency (V/f) changes due to software participation in power state changes.
AMD also addressed reports of instances where simultaneous multi-threading (SMT) is causing performance to dip in games. The company said it expects games to either benefit from SMT or see no change at all in performance. According to AMD, that is the case in several games, including Arma 3, Battlefield 1, Mafia III, Watch Dogs 2, Sid Meier's Civilization VI, For Honor, Hitman, Mirror's Edge Catalyst, and The Division. AMD also says that third-party testing backs its claim up.

All that said, AMD isn't leaving things entirely in the hands of developers.

"We have already identified some simple changes that can improve a game’s understanding of the "Zen" core/cache topology, and we intend to provide a status update to the community when they are ready," AMD said.

Via:  AMD
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