#UK Amiga in the U.S.
05-Aug-94 00:06:33
Sb: #42653-#UK Amiga in the U.S.
Fm: Brian Bartlett 72037,570
To: Michael Hendry 100015,2630
Michael,
if you look at the schematics, one of the signals generated by the
power supply is TICK, which is exactly at the same frequency as that of
the input power signal. TICK is normally used as the TBASE signal for
marking the passage of time. BTW, it is possible to use the _VSYNCH
signal in place of TICK, if your power supply drops TICK, but it is not
quite as accurate, and it happens to come from the video section.
In any case, if you run 60 Hz power into an Amiga set up for 50 Hz
TICK, you will get a fast clock. Hmmm, it might be possible, if it's on
that motherboard, to switch to using _VSYNCH. That's a thought, since it
will be 50 Hz no matter what.
What you might want to do is see if you have a jumper on the
motherboard near one of the 8520's, or find someone that knows the exact
jumper for your machine. I don't have a schematic for yours. In either
case, you may want to switch it to use _VSYNCH for the duration of your
stay here. It's not exactly accurate, but much more accurate than that of
a TICK derived from 60 Hz.
BTW, mostly wrong <g>. I've only chased this signal around the
schematics a half dozen times, or so. It was a common problem, at one
time, for a whole series of A2000's; TICK would die in the power supply.
"You do trust me, don't you? Of course you do."
— "To Play the King" (BBC)