Re: VIC - DRAM-refresh

From: Marko Mäkelä (
Date: 2001-05-16 10:03:36

On Wed, 16 May 2001, Ruud Baltissen wrote:

> Nick came up with the CAS-before-RAS (CBR) as well. The advantage of CBR is
> that you don't have to worry about an own refresh counter. But then we still
> must do it on a moment that the VIC performs the refresh for the onboard
> RAM. Detecting BA as John suggested probably is not accurate enough. And
> don't forget about the differences between PAL and NTSC.

You could detect the beginning of the scanline and count Phi2 cycles after
that.  The refresh cycles are always at the same position relative from
the beginning of the line.  And as far as I know, there are three VIC-II
compatible video chips with different timings: 6567R56A and earlier,
6567R8 and later (NTSC), and 6569 and later (PAL).


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