Wow. This is super odd. The time machine backup and supplemental update have nothing to do with the severe performance degradation I’m seeing with the W5700X. It has something to do with running the geekbench Metal Compute benchmark while Safari is running. Note that I have a couple of stopped videos in Safari.
If I run the OpenCL test with Safari running then performance is fine, even with multiple runs. But as soon as I run the Metal test with Safari running, performance dies. And it stays dead even if I quit Safari. And even the OpenCL performance stays dead! However, a reboot fixes the problem.
So something bad is going on under some circumstances. Ah. It’s the stopped videos! Wow! I closed both video windows and now performance is stable for the Metal test, even with Safari running.
So kids, beware of using Metal if Safari has a window that contains a video, even if it’s stopped! Performance will dive, and may require a reboot to get it back.
[edit] Oops. Even with the video windows closed, performance is still bad if the Metal test is run with Safari running. It seemed to behave, but now it isn’t.