I think it can register as much as you can throw at it. I seem to recall booting my 4000 with a 1.3 rom through a program like 'TUDE and tossing in a 1.3 workbench disk and seeing the accurate 66 megs free or so. (64 fast, 2 chip) Pretty impressive foresight. (Of course, I couldn't read my IDE controller in 1.3, but hey...)
