The PTCH patch, being based on ROM version number, is the same for a lot of machines. For example, the IIci through Quadra 630 (minus the AV macs) share the same version number. So the Performa 475 already has a patch that will get run, although it predates any knowledge of teh 475, its ROM, processor, or MMU. If it didn't find the patch, it would have displayed the "This is a 'Minimal' system install and doesn't include bits for this machine" or something along those lines.
The patch gets pretty complicated since it runs on so many different machines, but among other things it sets up a bunch of Gestalt values based on various pieces about the system and installs or replaces a bunch of A-Traps.
FWIW, I got a flickering "Welcome to Macintosh" when my ever reliable floppy saved a 0 sized PTCH resource ID 0. I think it's reasonably safe to assume flickering dialog == some sort of crash.
The patch gets pretty complicated since it runs on so many different machines, but among other things it sets up a bunch of Gestalt values based on various pieces about the system and installs or replaces a bunch of A-Traps.
FWIW, I got a flickering "Welcome to Macintosh" when my ever reliable floppy saved a 0 sized PTCH resource ID 0. I think it's reasonably safe to assume flickering dialog == some sort of crash.