Tony Mantler wrote:
>At 2:33 PM -0500 9/4/2000, Peter wrote:
>[...]
>>How does one install a new card in a Mac ..?, I mean with that interrupt
>>scheme
>>the driver must first be installed, before the card can be inserted .. ?
>>The other way should halt MacOS.
>
>The driver stored on the ROMS in the NuBus card are loaded by the mac rom
>on bootup.
>
>This interesting feature does let you do a few neat things, though, like
>put in a card that loads a full featured debugger before the system is
>launched from disk.

So if the bootloader uses the system ROM to download and run on-card ROM then
at least the card should stop annoying the system?, thus allowing a peaceful
netbsd loading ;)

>>>MacOS, of course, is perfectly happy to just call the slot int ack function
>>>to service the interrupts it gets. Unfortunatley, the slot int ack function
>>>is allowed to access any part of MacOS it pleases, so calling it from
>>>within another OS is not worth the trouble.
>>
>>Access how .. ?
>
>Like calling system functions, accessing low-memory globals, etc.

But these accesses, are they not controllable .. ?, a function in kernel space
can do many nasty things but they won't because they are designed what to do,
and so it should be possible to do with these things too.
A computer does what it is instructed to. (Maybe exception for Mac's then :-)

Anyway, is there any other caveats to controll the Mac at boot time, except for
annoying interrupts?, any stuff that will mess a running program,
if the program can't controll anything is another story.

What I know only IRQ, NMI, DMA. Can disturb a running computer program in a
normal enviroemnt. So if IRQ's are told to shut up. DMA is nonexistent. And
hopefully nothing triggers NMI except for things like parity error on RAM or
similar. One should have a working instruction execution.

          /Peter