#
# SYNCFIX.PRG:
#
# A software patch for the Falcon VGA hardware-sync problem.
#
# (C) 1995 Douglas Little / BSS

While testing a set of image viewers for Apex, we discovered that
they had trouble with some 14-inch VGA monitors - which resulted
in a strange 'flickering' or slowly 'alternating' image. The Apex
viewers use software trickery to allow 24-bit displays on a
standard Falcon and since we could find no fault with the code,
it was getting obvious that something about the Falcon / monitor
combination was the root of the problem.

After some investigation, we found that there was indeed some
kind of obscure hardware problem and that it was causing the
Falcon to produce extra vertical-blank (screen refresh) interrupts
for no good reason at all. Now although this problem is not fatal,
it does result in the unnecessary (multiple) re-running of several
areas of the Falcon's ROM which can cause timing problems and
steals a little of the 68030's valuable processing time.

The purpose of this patch is to re-vector the vertical blank
interrupt towards an early death for all but the very first pass
in each refresh - in other words, it means the interrupt only
does anything purposeful once in every 1/50th of a second -
instead of 'as many times as it likes'.

The result of this patch is a more stable operating system and
an ever-so-slightly faster machine.

This patch only of use to those people with a troublesome VGA
monitor / Falcon030 combination. I have supplied a self-test
analyser (SYNCTEST.TOS) to distinguish between the machines that
DO need the patch and the machines that DON'T.

The self-test program must be allowed to run for a few seconds
before it can determine in absolute certainty that your machine
doesn't need the patch, although running it a few times won't do
any harm just to be sure! I would also suggest trying it out in
a number of different video modes as it is still unclear exactly
what is causing the dirty monitor signals.


Standard disclaimer:

This software has been well tested and to the best of our
knowledge contains no bugs or other such nasty surprises, however
since there is no way to ensure absolute certainty that our
program will not cause problems on any one computer system, we
must warn that neither myself (Douglas Little) nor Black Scorpion
Software can be held responsible for any damage or loss of data
caused by the use of this program  - either directly or indirectly
- (however unlikely) and we would strongly suggest that if anyone
has doubts about the safety of this program then they should
refrain from using it on their system.


Beyond all that, we hope you find this patch ulimately helpful....

:)

Douglas Little @ BSS