Re: NTSC VIC-II timing

Date: Wed, 21 Jun 2017 18:34:58 +0200
Message-ID: <7114698.pjo96ZXAp5@rakete>
On Wednesday 21 June 2017, 19:27:48 Marko Mäkelä <> wrote:
> On Wed, Jun 21, 2017 at 04:40:03PM +0200, wrote:
> >According to the famous document by Chris Bauer, there are three timing
> >variants of the VIC-II. While PAL is always 63 cycles per  line, with
> >NTSC there can be either 64 or 65 cycles per line and I am in fact able
> >to reproduce the difference with -model ntsc and -model oldntsc in the
> >current VICE.
> You should have the 6567R56A and 6567R8 that I gave you, right?
> >The question (before I spend weekend on trial'n error counting cycles
> >and possibly reinventing the hammer ;-) is: do we have ane established,
> >reliable software method for detecting which NTSC VIC-II is installed
> >in the machine? I guess it must have been done multiple times by now
> >and used in some NTSC games/demos..
> The simple way is to disable interrupts and write a loop that samples
> $d012, counting the cycles that go between changes. I do not know if
> exactly such implementation is available anywhere.

i wouldnt call that exactly simple :) counting cycles always needs to be cycle 
exact code - which is far from that.

instead, simply check the number of scanlines - has a couple examples


Very few people do anything creative after the age of thirty-five. The reason 
is that very few people do anything creative before the age of thirty-five 
<Joel Hildebrand>

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Received on 2017-06-21 17:05:10

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