Re: Universal grammar

"Hans" == Hans Aberg <haberg@xxxxxxxxxx> writes:

>> In fact we can view the whole machine's memory as the reset
>> interrupt's interrupt server.

Hans> One should also be aware of that the early CPUs did not have
Hans> special treatment of IO (input/output) devices etc. Instead,
Hans> the computer manufacturer put some IO devices on specific
Hans> memory addresses, which the CPU could read and write
Hans> from. The chip hardware has since become more complicated.

You're talking about memory-mapped I/O. That's a separate dimension
from interrupts and DMA (direct-memory-access).

e.g. the Apple II does use memory-mapped I/O (because the 6502
microprocessor doesn't have a separate I/O port address space). But
it does support interrupts. PC's, using ix86 processors, do have a
separate I/O port address space, and earlier PC peripherals do use
that instead of memory-mapped I/O. They support interrupts, too.
(Later PC hardware do use memory-mapped I/O for better speed, though.)


--
Lee Sau Dan 李守敦 ~{@nJX6X~}

E-mail: danlee@xxxxxxxxxxxxxxxxxxxxxxxxxx
Home page: http://www.informatik.uni-freiburg.de/~danlee
.

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