AMD Ryzen 5000 L3 Cache Latency Issues Persist in Windows 11 Even After Patch Fix


One of many important highlights of Home windows 11 was the crippling bugs. The Ryzen CPU efficiency points have been a few 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 newest Zen 3-based Ryzen processors. The L3 cache latency deteriorated by as a lot as 6 occasions, adversely affecting the lows in video games. Sure latency-sensitive video games reportedly present a deficit of as a lot as 15% in some circumstances.

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

AMD had launched an announcement on social media stating that patches for the 2 points have been developed, and can be launched quickly. The patch for the Most popular Cores (UEFI-CPPC2) bug was speculated to be launched on the twenty first of October, whereas the L3 cache latency bug can be fastened through 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. Nonetheless, even after the newest OS replace (model KB5007215) which arrived this Tuesday, and a new chipset driver, the L3 cache latency stays removed from optimum.

German outlet, Heise performed checks 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 occasions. The L3 cache latency has additionally remained larger (than Home windows 10), which means that it’ll take one other spherical of patches from MS (or AMD) to repair the difficulty fully.

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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