In 2001 I was using a G4 with Mac OS 9.2 for Photoshop while working at a studio; that was Photoshop version 7, which is pre-CS (which started with 8.0). My memory of the workflow at that time was that most system operations were snappy as hell. Sure, there was a bit of load time for very large files and some of the operations had a bit of lag but there really became a point around that time that the speed of work that you could do for most operations essentially matched the speed of the machine. Before that era, I remember going to use the cloning tool on a large, high-DPI image and getting a lag as you dragged the brush over a spot... waiting for it to catch up. The G4, especially when we upgraded one with more ram and OSX (which also was a huge change that happened to coincide with the G4) is when I remember machines getting to the point where I wasn't waiting on lag all the time when working.
I used both a 1Ghz iMac G4 and 2Ghz iMac G5 (ALS model) in the 2000s for a lot of Photoshop work and remember them performing similarly. Both were excellent machines for that particular use case and zipped through anything I threw at them in PS, especially the G5 which I put 2GB of RAM in.
The PS versions I used were chiefly 7.0 and CS1, with some CS2 mixed in towards the end of the G5’s lifespan. I miss those versions so much because they sat at nearly a perfect nexus of features, responsiveness, and resource consumption. Such a stark contrast to PS CC.
