Path: utzoo!attcan!uunet!husc6!cmcl2!nrl-cmf!ames!pacbell!att!chinet!saj
From: saj@chinet.UUCP (Stephen Jacobs)
Newsgroups: comp.sys.atari.st
Subject: Turning off vertical blank interrupts
Keywords: interrupts traps vbl
Message-ID: <5888@chinet.UUCP>
Date: 26 Jun 88 02:56:46 GMT
Organization: Chinet - Chicago Public Access UNIX
Lines: 9

A while ago I asked what would happen if I set the interrupt level of an ST
high enough to disable the vertical blank interrupt.  The responses were
not unanymous, but I got the idea that there should be about a 5% speed
increase, against the possibility of crashing GEM.  I just tried it in a
computation-intensive GEM application.  The good news is no crash.  The bad
news is only maybe a 1% speed-up.  By the way: I tested that the vbl interrupt
was really disabled by flipping the switch that controls whether my Thomson
Ultrascan monitor is claiming to be color or mono: monitor change is detected
in the vbl routine.