🚀 go-pugleaf

Randell Jesup <jesup@cbmvax.uucp> writes in Message-ID: <6969@cbmvax.UUCP>

- In article <10949@behemoth.phx.mcd.mot.com> mph@behemoth.UUCP (Mark Huth)
- writes:
- > Well, I'm not Dave, but I'll jump in here.  Forbid in not too bad - just
- > eats processor doing nothing while the page swap occurs.  That is, we do
- > not care why the task forbids, we simply comply by not scheduling another
- > context.  If a page fault occurs, swap a page.  If it was the wrong page,
- > then you'll get another page fault, so you swap that one in.
-
-     Sorry, but every disk driver I've seen uses tasks, and therefore
- you MUST break the forbid in order to page, which means a page fault while
- forbidden is disaster.

Heh, a lot of people don't see the difference between the Amiga and another
computer such as the MacIntosh. The Amiga is a message-based multi-tasking
microcomputer. The keyword here is not only multi-tasking, but also message-
based. For any disk I/O which we want to perform, we have to send a message to
another task telling it to controll the disk. That means that if you have no
multi-tasking (we are in Forbid()/Disable() or in supervisor mode) we can not
pass any messages around.

On the MacIntosh, this would be no problem. Their disk handlers are not
separate tasks, but rather library routines executing under the context of the
task calling them.

Pop-quiz: On the MacIntosh, can you edit a file with WordPerfect while another
          program is reading the disk under MultiFinger? Heh? Can a MacIntosh
          multitask?

Valentin
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