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| From: Richard Atkinson
Date: 1999-09-23
Subject: Re: PAL-NTSC Crystal Switch
|
On Wed, 22 Sep 1999, Don Judy wrote:
> Fellow Plus/4 addicts,
> Since I now have access to a PAL
> compatible monitor...
> Would it be impossible to install a
> PAL crystal so it would be switchable
> with the NTSC crystal? Use a quiet
> switch so that I could do it safely
> after powering up and changing the
> value at $ff07 from NTSC to PAL?
> Otherwise I need to get a PAL ROM
> I guess and turn one of my Plussies
> into a full scale PAL machine.
Unfortunately switching crystals after power-up doesn't work, at least not on the VIC-II. The video chip gets confused and ends up in some sort of an undefined state, with the screen totally corrupted and the refresh rates all wrong. I suspect the same thing would happen with the TED. If you had two whole oscillator circuits and switched between them electronically
(ie. using a 1 of 2 selector), then this might work, but unfortunately TED has its crystal oscillator onboard.
I'll swap a PAL ROM for an NTSC ROM with you, though...
Do you need a PAL crystal?
Richard
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