I get really erratic beachballing in El Capitan. Every click or other action can cause beachballing from a few seconds to tens of seconds. This happens in all or most programs (for example Safari, Chrome, Office, Master Suite, Spotify). For example in Chrome it can be triggered by opening a new tab, writing a url or scrolling down a heavy web site. In Word just writing text can beachball for a few seconds. Some things I’ve noticed: The problem arrives only awhile after installing El Capitan I had the same problem with Yosemite but not in Mountain Lion (I skipped Maverics). It wasn’t this bad however The problem disappeared after updating 10.11.2 to 10.11.3 but resumed some days later The problem is possibly not as bad if I leave the Mac unused for 10-15 minutes after starting Closing down OSX is slower than it used to be even if all the programs are closed My Mac Pro: Mac Pro 4.1 (firmware updated to MP 5.1) W3690, 24 GB RAM, GTX 980 Ti, Dell UP2715K OWC Accelsior for OSX, Crucial m4 connected to the Accelsior through eSATA for Win10 I can’t start Apple Hardware Test for some reason. I’ve tried a different GPU and monitor, connecting the memory modules one at a time and I’ve of course unplugged all the external peripherals. Nothing has made a difference. I don’t believe there is something wrong with the hardware as Windows 10 runs flawlessly with consistent performance even in modern games. I’ve tried finding a problematic process/program from the activity monitor but I can’t find anything useful. Seems like the monitoring freezes during the beachballing - processor time and memory usage don’t spike according to the activity monitor. Any idea what can be wrong? I’m so frustrated and I’d still like to keep using the old war horse….. in OSX!