Re: 6561 (PAL VIC-I) interlace mode bit

From: Marko Mäkelä <>
Date: Fri, 26 Aug 2011 12:41:26 +0300
Message-ID: <20110826094126.GD2834@x60s>
On Fri, Aug 26, 2011 at 11:25:37AM +0200, Anders Carlsson wrote:
>Marko Mäkelä wrote:
>>If I remember correctly, my demo program would switch the display 
>>to an interlaced 8x16 font on the 6560.
>Hm, I always thought the interlace bit on the 6560 just toggles the 
>chip from producing 30 full (progressive) frames @ 60 Hz to producing 
>60 half (interlaced) frames. Does the perceived vertical resolution 
>really improve?

I would say that it does. Please try my test program. It switches the 
font on every half-frame, using a video-synchronized timer interrupt as 
a poor man's raster interrupt. I just checked that I do have the NTSC 
VIC-20 board in my collection. I kept the VIC-20s and C64s and C128s 
when Ruud and Patryk picked up the rest of my collection.

>On newer computers like the Amiga, interlaced mode really means double 
>vertical resolution at the cost of flicker unless you have a monitor or 
>flicker fixer than can handle it. I have read about NES and probably 
>also C64 units that produce a progressive video signal which some newer 
>TFT, LCD, Plasma etc TV's spew upon since they expect an interlaced 

Another reason to steer clear of that flat-screen garbage. The primary 
reason for me not to "upgrade" from CRTs is this counter-comment to a 
buy-more-stuff piece of news:

"Sure, you eliminate several kilos of leaded glass, but you replace it 
with LCD electronics and all the highly toxic compounds associated with 
that process. Crushed and submerged in water, leaded glass will not 
leech, but let the waste from LCDs soak in a stream and you'll soon find 
heavy metals downstream."

Best regards,


       Message was sent through the cbm-hackers mailing list
Received on 2011-08-26 10:00:24

Archive generated by hypermail 2.2.0.