Path: utzoo!utdoe!generic!pnet91!ericmcg
From: ericmcg@pnet91.cts.com (Eric Mcgillicuddy)
Newsgroups: comp.sys.apple2
Subject: Re: Multitasking on a II
Message-ID: <289@generic.UUCP>
Date: 17 Dec 90 00:50:09 GMT
Sender: root@generic.UUCP
Organization: People-Net [pnet91], Etobicoke, ON
Lines: 12

The 65C02 and 65816 have two uninteruptible instruction, TSB and TRB. These
are Test and Set (or Reset) Bit. Perhaps the *RESET line would prevent
interuption, but nothing else will stop them from completing their function
(usually marking a semaphore). Any subsequent accesses to the semaphore will
show it as being in use. I hope Prodos uses this for the "PRODOS_BUSY" flag
and for locking Handles. (?).

These instructions take 5-7 cycles to execute, so they damn well better work
as advertised, eh?

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