I had something similar, but not at the same level you experimented, and I am also havin i7 processor and win 7.
I went on Adobe Help, the section on Optimising Photoshop Cs 4, CS 5 , Windos 7 , Windows Vista http://kb2.adobe.com/cps/404/kb404440.html
and following all advises, particularli the setting of the Virtual memory and now ACR works properly.
I point out that I am NOT an expert on computer, but in my case, it worked.
Good luck and best regards
Many thanks for your reply.
I have previoulsy spent quite some time looking at the various recommendations Adobe give for performance and I think I've got my PC set up pretty well in respect of this. Having said that, I haven't adjusted any of the Windows virtual memory settings, so I might take a look at that later on. However, I'm not convinved this is the root cause of the problem: my memory use wasn't at 100% (just the processor), and as it was just one raw file on an 8GB system, I can't see how it could max out in the way it did... But then I'm not a computer expert either...
(Oh, you linked to the Mac performance page! Threw me for a minute there! )
Were you running the 32-bit version of Photoshop for some reason, which would have much less memory.
A good way to check if it was Virtual memory causing a problem, would be to start up TaskManager and add the Page Fault Delta column to the set that is displayed and see if that column has a large number in it while you're waiting.
You might also experiment to see if the same behavior happens on another RAW, meaning that when you adjust it, initially, things are ok, but when you re-open it, to adjust it, some more, things are very slow, and whether or not virtual memory page faults are involved.
No, it was definitely running the 64-bit version.
I'll do some more experimenting over the weekend and if I hit any issues, I'll use your advice on virtual memory monitoring. However I did do some experimentation last night once my PC had recovered, and the problem seemed to only be triggered when opening that one file with the heavy adjustment brush edit applied. But I agree that more testing is very much worthwhile.
Many thanks for your advice.