| From: Marko_Mäkelä
Date: 1998-05-27
Subject: Re: NTSC on PAL...
|
On Wed, 27 May 1998, Christian David Johannesdotter wrote:
> Once again...
>
> > The regular NTSC Plus/4's also don't have a significantly faster clock.
> > In PAL, the processor clock is derived from 17.773Mhz /10, and in NTSC,
> > 14.31818Mhz /8 which result in quite the same clock rates.
>
> Still, setting NTSC MODE on PAL plus/4s speeds up crunchers, fractal
> creators and other routines w/ many calculations to be done enormously.
Of course it does. The NTSC mode selects clock divisor 8, which makes
17734472/8 Hz double clock frequency. Similarly, setting PAL mode on NTSC causes the double clock frequency to be 14318181/10 Hz. But all video timings will be way off (by a factor of 10/8 or 8/10).
> It's also possibble to switch only parts of the "screen" to NTSC MODE and
> leave like one charline for controlling output data or something like
> that.
Yes, and according to Levente it has been done on the plus/4. I think that he sent me a routine (I think it was by someone else) that demonstrated this.
Marko
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