AMD’s SMT (Simultaneous Multithreading) and Windows 10 Scheduler
AMD’s SMT (Simultaneous Multithreading) preforms a similar function as Intel’s Hyperthreading. SMT permits multiple threads to be executed simultaneously on one core. In order to function properly in Windows, the CPU scheduler must know how to correctly scheduler threads for the best performance. It currently schedules all CPU cores the same, instead of giving the primary cores preference before the SMT cores. This is similar to the issues that happened when the first Intel dual core with hyperthreading CPU’s and the AMD FX series CPU”s were released. It appears that an update from Microsoft is forthcoming.
During most of our testing we saw better performance with SMT turned on over having SMT turned off. However, when an application uses more than one thread but less than the total number of CPU threads, there can be some performance benefits to turning SMT off. There were notable exceptions though, most notably Fritz Chess. Fritz Chess is just one example though. We expect many applications will see a notable increase in performance once Microsoft releases an update for Windows scheduler. In the meantime, we recommend leaving SMT turned on unless there’s a advantage to turning it off.