Path: utzoo!utgpu!water!watmath!clyde!att-cb!att-ih!chinet!saj
From: saj@chinet.UUCP (Stephen Jacobs)
Newsgroups: comp.sys.atari.st
Subject: Video interrupts: using or disabling
Keywords: interrupt vector priority speed
Message-ID: <3379@chinet.UUCP>
Date: 9 Mar 88 06:34:31 GMT
Organization: Chinet - Chicago Public Access UNIX
Lines: 11

I am curious about the horizontal and vertical blank interrupts.  How much
code can one safely put in a horizontal blank routine?  How many micro
seconds does each call of the default vertical blank handler take?  There
appears to be a flag telling the default vertical blank handler to cut its
operation short: what awful thing (if any) would happen if the interrupt
threshold was simply set above the vertical blank level?  And finally, how
do I try playing with these things (I've never done anything with privileged
instructions on the 68000, so those interrupt levels and first 1 K of memory
flags are new territory).  I have Mark Williams C (with their assembler
included), a few Abacus books and some 68000 documentation.  Use your best
judgement about whether to mail or post replies.