December 1, 2021

AMD Ryzen 5000 L3 Cache Latency Points Persist in Home windows 11 Even After Patch Repair


One of many primary highlights of Home windows 11 was the crippling bugs. The Ryzen CPU efficiency points have been a number of the better-known bugs. There have been two substantial points affecting the Zen household. The primary one elevated the L3 cache latency. Identified to have an effect on all Ryzen CPUs, from the 2nd Gen Zen+ to the most recent Zen 3-based Ryzen processors. The L3 cache latency deteriorated by as a lot as 6 instances, adversely affecting the lows in video games. Sure latency-sensitive video games reportedly present a deficit of as a lot as 15% in some instances.

Identified Discrepancy Impression  Repair
Measured and purposeful L3 cache latency might enhance by ~3X.   Purposes delicate to reminiscence subsystem entry time could also be impacted. Anticipated efficiency influence of 3-5% in affected purposes, 10-15% outliers attainable in video games generally used for eSports.  A Home windows replace is in improvement to handle this concern with anticipated availability in October of 2021.  
UEFI CPPC2 (“most popular core”) might not preferentially schedule threads on a processor’s quickest core. Purposes delicate to the efficiency of 1 or just a few CPU threads might exhibit lowered efficiency. Efficiency influence could also be extra detectable in >8-core processors above 65W TDP.  A software program replace is in improvement to handle this concern with anticipated availability in October of 2021.
Supply: AMD

AMD had launched a press release on social media stating that patches for the 2 points have been developed, and will likely be launched quickly. The patch for the Most well-liked Cores (UEFI-CPPC2) bug was speculated to be launched on the twenty first of October, whereas the L3 cache latency bug will likely be fastened by way of a future Home windows Replace scheduled to roll out on the nineteenth of October.

Quick ahead to the current day, and each Microsoft and AMD have already rolled out a number of updates to repair the L3 cache latency with Ryzen CPUs and Home windows 11. Nevertheless, even after the most recent OS replace (model KB5007215) which arrived this Tuesday, and a new chipset driver, the L3 cache latency stays removed from optimum.

German outlet, Heise carried out exams with AIDA64 utilizing a Ryzen 9 5950X and MSI B550M Mortar. The outcomes are inconsistent and nonetheless notably slower than Home windows 10 with the identical system. The learn and write speeds assorted considerably and the copy throughput additionally fell off a cliff at instances. The L3 cache latency has additionally remained greater (than Home windows 10), which means that it’ll take one other spherical of patches from MS (or AMD) to repair the difficulty utterly.

Home windows 11: Run 1 Run 2 Run 3 Run 4 Home windows 10
Learn pace 438GB/s 723GB/s 696GB/s 777GB/s 1047GB/s
Write pace 578GB/s 504GB/s 176GB/s 261GB/s 680GB/s
Copy Pace 218GB/s 203GB/s 689GB/s 681GB/s 912GB/s
Latency 11.3 ns 10.9 ns 10.6 ns 11.3 ns 10.3 ns

Supply: Heise

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