The MSI AGESA 1.2.0.2a update for AM5 motherboards introduced some latency issues on DDR5 memories, which the Latency Killer feature seeks to fix on X870E motherboards.
Most motherboard vendors have already released the AGESA 1.2.0.2a update, which offers full support for the Ryzen 9000X3D processors on the latest X870/X870E motherboards. Surprisingly, this update also caused some latency issues, which MSI has now fixed by adding a new feature.
As discovered by some users, the MSI X870/X870E motherboards added roughly 10ns of higher memory latency with the AGESA 1.2.0.2a update, which of course wouldn't be noticeable without actual testing. Thankfully, even though the difference is minor, MSI fixed it by adding the "Latency Killer" feature to its X870/X870E motherboards.
As reported by @unikoshardware, a user has notified that his MSI MEG X870E GODLIKE now has the option to turn on Latency Killer in BIOS. The feature has three options to choose from: Auto, Disabled, and Enabled, and as to how it helps in rectifying the problem, it is not clear yet. However, the feature did help in reducing the memory latency by around 8ns as shown by the same user.
This time, the motherboard used was the MSI MPG X870E Carbon Wi-Fi and the program used for benchmarking the memory kit was AIDA64. The latency went down to 66.7ns from 74.7ns on an EXPO-enabled 8000 MT/s memory with High Efficiency Mode(Tighest) enabled. As can be seen from the AIDA64 window, the update is done through the same AGESA 1.2.0.2a BIOS and users won't need to download a new one.
Unikos Hardware says that users don't have to roll back to the previous BIOS update to get back the original performance as the Latency Killer will do the same through the latest BIOS. The latency improvement did improve the scores on the AIDA64 benchmark noticeably, but in most applications, this won't be visible, including gaming.
One more thing to point out here is that the Killer Latency option in the BIOS mentions:
Enhances latency performance but could potentially reduce CPU performance.
This is weird, but we don't know how much of a performance impact users will see by turning on Latency Killer. As it says "Potentially", it's possible that the feature might not affect CPU performance at all. Still, we look forward to updates from users who are testing the new MSI feature.