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Originally Posted by kerravon
I'm not talking about Amiga OS, I'm talking about Amiga PDOS. For what reason can I not keep interrupts disabled on Amiga PDOS?
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Why would you even want to?
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Also, even if I do enable interrupts, how many different interrupts will the hardware generate?
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There are 6 interrupt levels, used by the serial port, timers, vertical blank, blitter, copper, disk controller and audio channels. If you take over the system you can get away with not using them, but then you must poll each device to see if it needs servicing.
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And I would actually expect that to have a default handler in the new BIOS. Right?
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Yes.
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I don't think the BIOS can have a requirement for the operating system to take ownership of interrupts by a particular point.
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The BIOS should be responsible for handling interrupts, as this is hardware that higher levels shouldn't have to know about.
The purpose of a BIOS is to virtualize the hardware. When you port an OS from one hardware platform to another, this is the part that needs to be written to handle that specific hardware. On a PC the BIOS is in a ROM on the motherboard, and any hardware differences are incorporated into it by the manufacturer. The Amiga's 'BIOS' is integrated into its multitasking OS and cannot easily be extracted, so to do what you want without any baggage you need a custom BIOS.
When porting from x86 to 68k, the compiler must also generate appropriate instructions to suit the CPU. A PC's BIOS is accessed via x86 software 'interrupts'. The 68000 can do something similar with traps. The Atari ST uses trap #13 to call its BIOS functions.