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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 ...


9

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 ...


6

Very briefly: The way harddisks are addressed changed over time. Originally, you'd specify cylinder/head/sector (CHS), then it switched to logical block addresses (LBA), and the commands for those went through various versions with an increasing number of bits. As you can read on Wikipedia, LBA first used 22 bits, then 28, then 48. So you need to distinguish ...


5

That BIOS screen clearly says that it detects the drive as roughly 8 GB. The parameters say 16383/16/63 as so this BIOS cannot detect or provide the extended disk services that would allow the drive to be used beyond the 16383 cylinders, or the 8GB limit. It does not matter if another program can detect the size properly by communicating with the drive ...


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