AMD said Windows 11 can cut game performance on Ryzen CPUs by 10 to 15 percent, and the operating system may not utilize AMD’s “preferred core” technology, but a fix in the works.

A support note on AMD’s web site published this week said Windows 11 may increase L3 cache latency a whopping threefold, which can cause slowdowns in latency sensitive applications. Lighter duty, cache-sensitive games might see a 3 percent to 5 percent hit, and lighter-duty games as e-sports titles could see frame rates drop from 10 to 15 percent.

AMD also said its “preferred core” feature, which tells the operating system which core in each CPU can hit the highest clock, also doesn’t work right in Windows 11. Each CPU is tested to see which core will run the fastest at the factory and is marked so the OS will dispatch tasks to that “preferred core.” Since Windows 11 doesn’t seem to work with it right now, any performance bump from using the best core wouldn’t happen. The company said the performance cost would be most noticeable in CPUs with more than 8 cores and with TDP ratings above 65 watts.

AMD said both Microsoft and it are working on an update to Windows 11 that should address both issues this month.