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35

The early Apple Macintosh computers (original Mac, Mac 512K, Mac Plus) all came with a "Programmer's Switch" installed on the side. Yes and no. While the switch was there, it was on the inside, so, not really accessible. Only after being 'enhanced' with the so called 'Programmers Key Aid', a snap on after market piece of plastic, griping into the ...


22

The "programmer's switch" is more technically known as the NMI (Non Maskable Interrupt) switch. It is mapped to a priority 7 interrupt on the 68K CPU, which means it is capable of interrupting anything besides another priority 7 event. When pressed, the CPU saves all its state on the stack, switches to privileged mode, then looks at the interrupt ...


4

It is rather straight-forward, technically speaking, to share both 3.5" floppy disks and their image files between a Classic Mac (e.g. MacOS System 7) and an Apple IIgs. This because both systems support ProDOS floppies and HFS floppies (in GS/OS), and both systems support image files for 800KB disks using DiskCopy 4.2. So, that solves most needs back ...


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