6561 (PAL VIC-I) interlace mode bit

On Thu, Aug 25, 2011 at 09:32:50PM +0200, Segher Boessenkool wrote:
>>In the NTSC VIC-I, there is a bit for enabling interlace mode. It does 
>>not work in the PAL VIC-I.  I wrote a test program for it: look for 
>>interlace.prg and interlace.tar.gz at 
>>http://zimmers.net/anonftp/pub/cbm/vic20/programming/.
>
>We have a 6561 as well...  Let's see, reg 00 bit 7...  It's wired up, 
>goes to the Y decoder, and the one output from there is wired up as 
>well.  I don't have further details, I haven't fully reversed this chip 
>(yet).  I guess the interlace doesn't work as intended, but it's still 
>there?

I don't remember if the bit remembers its contents, but it definitely 
causes no visible effect in the 6561. The picture is never interlaced.  
If I remember correctly, my demo program would switch the display to an 
interlaced 8x16 font on the 6560.

	Marko

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