I'm having this problem too, it started last summer I think, I assumed the problem would go away when it didn't I tried all sorts of things to make it stop. I'm using a MacBook Pro Retina and doing everything on SSD now but when I'm in the develop module I'll go to 400% or sometimes 600+% CPU the fan turns on and I see the pinwheel if I try to go to the next photo or set a star rating.
Things I've tried.
- Getting rid of spinning disks, move stuff to SSD and unmount the drives
- Starting a new catalog
- Killing all other running applications on the system
- Turn off mobile sync
- I used a newer MBP with a 512 SSD (both have 16GB of ram)
Getting rid of FW and USB3 drives helped the most but I don't want to see the pinwheel when I'm trying to select photos from a 1600 photo event or work on the 200 that I end up going with. I remember the first LR4 that I started using didn't have this problem. As I type right now I hear the fans speeding up and Adobe is back on top of my top command running behind this browser.
