23 Nov
2006
23 Nov
'06
9:01 a.m.
On 23 Nov 2006 at 10:13, Pete Turnbull wrote:
Because there's no effective way to time-slice or
multitask arbitrary
programs. The Z80 card won't voluntarily give up control on a regular
basis, and the Apple ][ doesn't support interrupts.
Hmmm, that would put the kabosh on doing it preemptively, but one
could still switch processors on entry to I/O requests, I suppose.
It wasn't that the Apple didn't support interrupts--the signals were
certainly present on the peripheral bus. It was that Apple didn't
think too hard about making use of the facility until the ][c came
out, then offered a firmware upgrade with an interrupt handler on the
][e (along with 80 column mode).
Cheers,
Chuck