Windows 11's First Patch Tuesday Gimps Ryzen CPUs Even More, Fix On The Way

lisa su holding ryzen topimage
Windows 11 hit the ground running last week—or maybe stumbling, at least on AMD Ryzen-based systems. As we reported at the release of the new operating system, CPUs based on AMD's Zen architecture are seeing drastically-worsened L3 cache latency under Windows 11. Yesterday was the first "patch Tuesday" for Microsoft's new baby, and lo and behold, the issue is... worse?

Indeed, after yesterday's updates, users on tech forums have noted that L3 cache latency is even worse for Ryzen systems. TechPowerUp reports that a Ryzen 7 2700X test system went from 10ns in Windows 10 to 17ns latency on Windows 11's release, and yesterday's update increases that figure to an absolutely awful 31.9 nanoseconds.

While an increase of almost 22 nanoseconds probably doesn't seem like a big deal—nanoseconds are quite short, after all—a tripling of L3 cache latency has a humongous impact on single-threaded performance for Zen processors. AMD's chiplet-based processors rely on their large L3 caches to mask performance penalties caused by relatively high main memory latency, particularly when compared to their Intel competitors.

tpu before after latencybenchmarks inline
Source: TechPowerUp

The L3 cache latency issue isn't the only problem facing Zen CPUs in Windows 11, either. There's also a problem with the power profile that breaks the UEFI Collaborative Power and Performance Control (CPPC) functionality, making the Windows scheduler unable to tell which CPU cores are the "best" cores that can clock the highest, further reducing peak single-threaded performance.

AMD has already announced that fixes for both issues are on the way and expected to be released later this month. Other reports around the web pin the release dates at October 19th for the L3 cache latency issue, while a new power profile for the CPPC issue will purportedly be produced on October 21st.

However, these reports all seem to stem from a Reddit post by user destiny2sk, itself a screenshot of a post on the forums by user "GoforceReloaded." It wouldn't be the first time (or the tenth time) that information like this was leaked, but given the sourcing we'd take those reports with a grain of salt. Hopefully the information is correct, as that would likely mean that the updates will be in place (and ensuring fair comparisons) for launch-day reviews of Intel's forthcoming Alder Lake platform.
Tags:  AMD, ryzen, windows 11