AMD is reportedly working on a new BIOS patch that will help improve inter-core latency on Ryzen 9000 “Zen 5” desktop processors.
AMD Ryzen 9000 'Zen 5' CPUs to Get Further Improvements as Red Team Plans to Release BIOS Patch to Improve Inter-Core Latencies
AMD's Zen 5-based Ryzen 9000 Desktop processors didn't deliver the performance boost we were expecting. While poor optimization for Windows 11 can be attributed to one reason, it's not the only one. Unoptimized core parking is one of the culprits, leading to lower-than-ideal performance, presumably due to unfinished software and BIOS support.
Geekerwan: AMD to fix Zen 5 C2C latency issue.https://t.co/v1ru4UXQmS pic.twitter.com/3u0pAmBuwV
— HXL (@9550pro) August 27, 2024
IN Ryzen 9 9950X Review by AnandtechThe Zen 5 CPU was found to have significantly higher inter-CCD latency than its predecessor. This is despite the Zen 4 and Zen 5 CPUs using a similar I/O die and infinity matrix design. However, a recent Geekerwan report on Bilibili (by using @9950pro) suggests that AMD is working on a solution to this issue with a future BIOS patch.
Inter-CCD latency is how quickly data or instructions are transferred between two Zen 5 CCDs (Core Complex Dies) in Ryzen 9000 processors. This structure is used to communicate with multiple chiplets such as CCDs and IODs. Since the Ryzen 9 9950X and Ryzen 9 9900X contain two CCDs, each carrying 8 Zen 5 cores, programs that use more than 8 cores must transfer data between the CCDs to run faster.
Unfortunately, unlike its predecessor, the Ryzen 9 7950X, the AMD Ryzen 9 9950X has almost twice the CCD-to-CCD latency of its predecessor. The average inter-CCD latency for Zen 5 is 180ns on average, compared to 76ns for the 7950X. This results in slower data transfers between CCDs, which results in slower multi-threaded performance in some workloads than expected.
The higher latency between CCDs is not due to the die design, but to AMD's unfinished, unpolished optimizations in the chipset's BIOS and software stack. As suggested by the new report, AMD will fix the high latency between CCDs with a BIOS update due in the coming months.
Hopefully we will see some performance improvements with the new update, but the exact date of the BIOS update is not yet known. However, this fix will not necessarily affect gaming performance, since most games do not use more than one CCD containing 8 cores. In programs that can use more than 8 cores, fixing the latency between CCDs may solve some performance issues.
Just yesterday AMD announced that they are bringing Optimizing Branch Prediction in Windows 11 23H2 via Backportingwhich will result in some performance gains, as seen in Windows 11 24H2. So it's clear that AMD probably rushed the release of the unfinished Ryzen 9000 series, which needs more optimizations to deliver significant generational improvements.
News source: Notebookcheck