Cool, sorry I forgot to explain the bootloader. Now that you've got it installed, for future updates you can copy femu.bin to your SD card, and then press Reset while holding PREV and SELECT. The ISP programmer isn't needed.
Good news! After many hours of scouring the web for ancient system software, and converting it to the right disk image format, all the 400K disk images I tried worked great on my Mac 512K:
System 2.0
Bootable MacPaint (system 2.0)
Bootable MacWrite (system 2.0)
System 3.2 HD 20
System 3.2 Installer
The only disk that doesn't work is that Disk011.dsk. I need to try copying that to a real floppy, and booting my 512K with that, to see if it's the disk contents or the Floppy Emu at fault. But at the moment the 512K's floppy drive is out of commission, so I need to get that working before I can try it.
Good news! After many hours of scouring the web for ancient system software, and converting it to the right disk image format, all the 400K disk images I tried worked great on my Mac 512K:
System 2.0
Bootable MacPaint (system 2.0)
Bootable MacWrite (system 2.0)
System 3.2 HD 20
System 3.2 Installer
The only disk that doesn't work is that Disk011.dsk. I need to try copying that to a real floppy, and booting my 512K with that, to see if it's the disk contents or the Floppy Emu at fault. But at the moment the 512K's floppy drive is out of commission, so I need to get that working before I can try it.