sometimes it recovers what I was working on, it often does not.
I'd think so but at the apple store they tested and said hardware's good; Adobe said outdated GPU but all drivers are updated when Apple updates OS so it's not that either. I have saved screenshots of many crash reports. Some are Adobe and some Apple. This only started three or four months ago, I've been running large (up to 2 GB) graphics files for years on this mid 2011 iMac with 12 GB RAM and AMD Radeon HD 6970M. Adobe also recommended turning off graphics processor, which didn't fix it but did slow things down - I can watch the erase follow the cursor, same with brushes.
Adobe changed something to make Photoshop less compatible with the iMac a few months ago, did they not? driver updates with every OS update. Card is AMD Radeon HD 6970M 1024 MB, 12 GB additional memory installed. All this worked FINE until about June. I had Apple check the hardware, they say it is fine and the problem is in Photoshop. I've erased the hard drive and restored without Pshop preferences a couple of times, uninstalled and reinstalled Photoshop a couple of times also. What's up with this? Is the mid 2011 iMac 27" really not enough computer to run Photoshop anymore?