Re: Article PC-card

From: Marko Mäkelä (
Date: 2001-04-04 15:38:18

On Wed, 4 Apr 2001, Ruud Baltissen wrote:

> I'm not sure if the VIC chip steals cycles but it at least needs to access
> the video- and colorRAM to build up a screen. And just for this reason alone
> it needs to be able to master the bus.

In the VIC-20, the VIC-I is the only chip that uses (transparent) DMA.  
Since the dot clock is only 4 times the bus clock, the VIC-I has 2 bus
accesses per displayed 8 pixels.  There are no bad lines, since both the
attributes (color and character codes) and the graphics (character
graphics data) are fetched on each line.


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