AMD To Provide Patch That Improves Ryzen 9000 “Zen 5” Inter-Core & Chiplet Latency

AMD is reportedly working on a new BIOS patch that will help improve inter-core latency on Ryzen 9000 "Zen 5" Desktop CPUs.

AMD's Zen 5-based Ryzen 9000 Desktop CPUs didn't provide the performance uplift we all expected. Even though one of the reasons for this can be attributed to the poor optimizations for Windows 11, it's not the only reason. The unoptimized Core Parking is one of the culprits resulting in slower performance than ideal, supposedly due to the unfinished software and BIOS support.

Geekerwan: AMD will fix Zen 5 C2C latency issue.https://t.co/v1ru4UXQmS pic.twitter.com/3u0pAmBuwV

— HXL (@9550pro) August 27, 2024

In Anandtech's review of the Ryzen 9 9950X, it was found that the Zen 5 CPU had significantly higher inter-CCD latency compared to its predecessor. This is despite both Zen 4 and Zen 5 CPUs sharing a similar I/O die & infinity fabric design. However, a recent report by Geekerwan at Bilibili (via @9950pro) suggests that AMD is working to address this issue through a future BIOS patch.

The inter-CCD latency is how quickly the data or instructions are transferred between the two Zen 5 CCDs (Core Complex Dies) within the Ryzen 9000 CPUs. This fabric is used for communication with multiple chiplets such as CCDs and IODs. As the Ryzen 9 9950X & Ryzen 9 9900X contain two CCDs, with each CCD carrying 8 Zen 5 cores, the programs that utilize more than 8 cores need to have the data transferred between the CCDs for faster execution.

Unfortunately, unlike its predecessor Ryzen 9 7950X, the AMD Ryzen 9 9950X has almost twice the CCD to CCD latency compared to the former. The average inter-CCD latency for Zen 5 averages at 180ns compared to 76ns on the 7950X. This results in slower data transfer between the CCDs, resulting in slower multi-threaded performance in some workloads than expected.

The higher inter-CCD latency is not due to the die design but due to AMD's unfinished, unpolished optimizations within the BIOS and chipset software stack. As suggested by the new report, AMD will fix the high inter-CCD latency via a BIOS update which should roll out in the coming months.

Hopefully, we will see some performance gains with the new update but the exact date for the BIOS update is not yet known. This fix, however, won't necessarily affect gaming performance as most games don't utilize more than one CCD containing 8 cores. In programs that can utilize more than 8 cores, the inter-CCD latency fix can resolve some performance issues.

Just yesterday, AMD announced that they are bringing branch prediction optimizations to Windows 11 23H2 via backporting, which will result in some performance uplift as seen with the Windows 11 24H2. So, it's evident that AMD has probably rushed in launching an unfinished Ryzen 9000 series, which needs more optimizations to provide some significant generational uplifts.

News Source: Notebookcheck