Now there you have a point. There was a lot of copy protection on the early Mac, and some of those fiddled around with the disk speed, which you could do on a 400K drive, but NOT on an 800K. It wasn't the ROMs that were incompatible, it was other hardware. Some devices depended on power from the 9-pin serial ports, which was not available from the 8-pin DIN port. There was so much bad copy protection which broke the software with every OS release, every new piece of hardware, etc. that users quit buying anything that smelled of protection. Developers got really sick of all the tech support, too. This applied in spades to games, and I keep forgetting that there are a lot of people on this forum whose only interest is old games.

The really remarkable thing is that most of Microsoft's Mac software retained compatibility, even though MS didn't use the documented APIs. They thought they were so much smarter than Apple's programmers that they wrote their own code to replace most of the toolbox. This did result in such ugly messes as Excel needing to run in the bottom 1 MB of memory, so when Excel launches under MultiFinder, Mac OS quits all other apps, saves their states, opens Excel, then re-launches the other apps and restores their states. Excel was important enough that Steve couldn't just ban it from the system as he's done with Flash on the iPhone.