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AMD dismisses Windows 10 Ryzen thread scheduling concerns

AMD dismisses Windows 10 Ryzen thread scheduling concerns

AMD has denied that there's anything wrong with the Windows 10 thread scheduler, dashing hopes that a patch from Microsoft could unlock further performance gains from Ryzen chips.

AMD has claimed that reports suggesting Windows 10's thread scheduler is responsible for lower-than-expected highly-threaded performance scores on its latest Ryzen processor family are inaccurate, pouring cold water on hopes a patch from Microsoft could further boost the chips' speed.

While reviews of the AMD Ryzen 1800X, 1700X, and 1700 Zen-architecture eight-core 16-thread processors have shown a considerable improvement in performance over their last-generation predecessors, there have been some statistical anomalies that reviewers have been scrabbling around to explain. One of these is a strange drop in performance when running Windows 10 compared to Windows 7, something some reports have claimed is evidence of an issue with the thread scheduler in Windows 10 failing to properly prioritise the physical cores over the virtual cores and spreading threaded tasks over the two four-core blocks that make up the chip - either or both of which would indeed harm performance. AMD, though, says that it has found no evidence to suggest that this is the case, and that any difference between Windows 10 and Windows 7 performance is likely to be down to the operating systems' internal architectures and not evidence of a scheduling issue.

'We have investigated reports alleging incorrect thread scheduling on the AMD Ryzen processor,' AMD's Robert Hallock explains in a community update published late last night. '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 utilising the logical and physical configurations of the architecture.

'We have reviewed the limited available evidence concerning performance deltas between Windows 7 and Windows 10 on the AMD Ryzen CPU. We do not believe there is an issue with scheduling differences between the two versions of Windows. Any differences in performance can be more likely attributed to software architecture differences between these OSes.'

In other words: according to AMD the Windows 10 thread scheduler is operating correctly and there's nothing for Microsoft to patch, leaving those who had hoped the Ryzen performance would be lifted further by a scheduler update - possibly even one which was originally due to be released in the cancelled February Patch Tuesday - disappointed. Elsewhere in the post, Hallock reports a flaw in the Sysinternals Coreinfo utility which generates incorrect topology data for Zen-architecture chips, data which have been used by some technology news outlets to support the theory of the Windows 10 scheduling issue. Upgrading to Coreinfo v3.31 or later, Hallock claims, will fix the bug.

Hallock has also detailed an interesting quirk of the X-family processors, the Ryzen 7 1800X and Ryzen 7 1700X: their temperature reporting features a fixed +20°C offset not present on non-X chips, meaning that a 1700X at the same temperature as a 1700 will report its temperature as 20°C higher. According to Hallock's explanation, the offset allows all Ryzen processors to share a single fan speed policy - though whether the offset will affect features like thermal throttling is not revealed.

Finally, Hallock addresses the issue of simultaneous multithreading (SMT), the technology which allows the eight-core processors to run 16 threads simultaneously. While some reviews have discovered that enabling SMT results in a drop in game frame rates, AMD's internal research is claimed to suggest the opposite. 'Based on our characterisation of game workloads, it is our expectation that gaming applications should generally see a neutral/positive benefit from SMT,' Hallock claims, detailing games including Arma 3, Battlefield 1, Mafia III, Watch Dogs 2, Civilization VI, Hitman, Mirror's Edge Catalyst, and The Division as either having no performance change at all or benefiting from the presence of SMT.

Hallock's post can be read in full on the AMD community site.

15 Comments

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Corky42 14th March 2017, 10:43 Quote
So basically all those statistical anomalies that reviewers identified are just in their imagination, good one AMD.
Harlequin 14th March 2017, 10:53 Quote
Quote:
Originally Posted by Corky42
So basically all those statistical anomalies that reviewers identified are just in their imagination, good one AMD.
That not what they said at all? AMD commented the scheduler is working as intended (as linus and pcper have demonstrated) . What both of those have said though , is the cahce reporting is `weird` and a driver is needed to fix that
Corky42 14th March 2017, 11:46 Quote
That not what they said at all, IIRC linus and pcper said it's working as intended but probably isn't working optimally for the unique architecture of Ryzen.

Besides that's just one of the many statistical anomalies that reviewers have highlighted.
Harlequin 14th March 2017, 13:03 Quote
Video with their conclusion.
https://youtu.be/6laL-_hiAK0?t=26m23s

http://image.prntscr.com/image/5d6bf457c6084db9bd19638c519f79c2.png



Other's have reported that before. Hardware.fr disabled one CCX, and ended up with a 20% performance increase in Battlefield 1, and around 3-8% in other games.


http://www.hardware.fr/articles/956-24/retour-sous-systeme-memoire-suite.html

http://image.prntscr.com/image/57d46709a9eb4491aa4cd9a568a854e8.png

lifted from

https://forums.overclockers.co.uk/posts/30603489/
Anfield 14th March 2017, 13:35 Quote
Quote:
Originally Posted by Harlequin
Other's have reported that before. Hardware.fr disabled one CCX, and ended up with a 20% performance increase in Battlefield 1, and around 3-8% in other games.

They had the Ram at 2400 (most likely due to the issues from immature bios versions plaguing Ryzen), the gap should be far smaller if they would have used 3000+ due to the speed of the connection between the two CPU modules being derived from memory clock speed.
Corky42 14th March 2017, 13:39 Quote
Quote:
Originally Posted by Harlequin
Video with their conclusion.
https://youtu.be/6laL-_hiAK0?t=26m23s

Other's have reported that before. Hardware.fr disabled one CCX, and ended up with a 20% performance increase in Battlefield 1, and around 3-8% in other games.

http://www.hardware.fr/articles/956-24/retour-sous-systeme-memoire-suite.html

lifted from

https://forums.overclockers.co.uk/posts/30603489/

And if you listened to the video when i posted it in the Ryzen benchmark thread you'd know earlier (18:45) they said (paraphrasing) that while the Windows scheduler is working as expected that doesn't mean it's working optimally for Ryzen.
Anfield 14th March 2017, 13:41 Quote
Yep, not broken doesn't mean it is as good as it could be.
rollo 14th March 2017, 13:41 Quote
Well it seems like it won't be fixed reading the post
sandys 14th March 2017, 13:56 Quote
If you admit to an issue you don’t have a solution to yet, you’ll put people off buying, as it stands, it’s actually pretty good and will be a good purchase, you don’t won’t people holding back waiting for a bug fix.
rollo 14th March 2017, 14:58 Quote
The kind of people buying Ryzen probably have a clue what's going on enough to read these sort of forums ect
Yadda 14th March 2017, 15:03 Quote
But if it isn't Windows 10's fault, who's going to get the blame now? :p
RedFlames 14th March 2017, 15:33 Quote
Reading AMD's statement just conjures this in my mind:

http://i.imgur.com/ciCcK2m.gif
Wakka 14th March 2017, 15:45 Quote
Quote:
Originally Posted by Yadda
But if it isn't Windows 10's fault, who's going to get the blame now? :p

Brexit?


Trump??


Kanye???
RedFlames 14th March 2017, 15:53 Quote
Quote:
Originally Posted by Wakka
Brexit?


Trump??


Kanye???

Jeremy Corbyn

The Boogie

Intel

Obama

The fact the day ends in Y

the possibilities are endless...
impar 15th March 2017, 11:21 Quote
Greetings!

You should also read the other blog post. Bunch of suggestions, this one is the more interesting one:
Quote:
Tips for Building a Better AMD Ryzen™ System
...
Throughout this process we also discovered that F1™ 2016 generates a CPU topology map (hardware_settings_config.xml) when the game is installed. This file tells the game how many cores and threads the system’s processor supports. This settings file is stored in the Steam™ Cloud and appears to get resynced on any PC that installs F1™ 2016 from the same Steam account. Therefore: if a user had a 4-core processor without SMT, then reused that same game install on a new AMD Ryzen™ PC, the game would re-sync with the cloud and believe the new system is also the same old quad core CPU.
...
https://community.amd.com/community/gaming/blog/2017/03/14/tips-for-building-a-better-amd-ryzen-system

Are you seeing reviewers re-download games for each system they test?
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