Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!jarthur!nntp-server.caltech.edu!toddpw
From: toddpw@nntp-server.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: Multitasking on a II
Message-ID: <1990Dec20.184254.16292@nntp-server.caltech.edu>
Date: 20 Dec 90 18:42:54 GMT
References: <289@generic.UUCP> <1990Dec20.143649.11598@world.std.com>
Organization: California Institute of Technology, Pasadena
Lines: 16

Prodos 8 has a busy flag.

Prodos 8 runs on a 6502.

Therefore, the 6502 has some kind of instruction that can be used for busy
flags. (In the case of Prodos 8, it's LSR/ROR.)

The IIgs toolbox and firmware, by the way, use INC/DEC. Look in the firmware
reference on page 270, and disassemble the routines pointed to by e1/64 and
e1/68. Whoever said INC/DEC were useless for this should go back to school.

Uninterruptable instructions are not even necessary for this sort of thing,
but they do make it a lot easier.

Todd Whitesel
toddpw @ tybalt.caltech.edu