I fondly remember playing with Photoshop 2.5 on my Color Classic with its 16MHz CPU with 10MB RAM... It was amazing what you could do on such a "primitive" machine.
Photoshop was a little bit of a masterpiece back then (it arguably still is, deep down) -- it had it's own 'swap' system for large pixmaps that allowed you to work on images that were massively bigger than the onboard memory; and it wasn't even that slow (unless you were applying filters on the whole image).