Re: System ROM 901227-01 wanted

From: Marko Mäkelä (
Date: 2005-10-30 21:26:48

On Mon, Oct 24, 2005 at 01:36:08PM +0200, Spiro Trikaliotis wrote:
> Hello Marko,
> * On Mon, Oct 24, 2005 at 11:30:26AM +0300 Marko Mäkelä wrote:
> > > Is this really a bug? I tend to disagree. It should not matter which
> > > background color is set. It is just the VIC-II which had an error in
> > > early releases, and this change was a work-around for that problem.
> > 
> > Which VIC-II revision?
> Well... I thought I could look up the net where I found that the -01
> ROM's problem is "only" a problem of the VIC-II, not of the ROM itself.
> Unfortunately, I could not find that article anymore.
> Does anyone here know what article I am speaking about? ;)

I do remember something like that, but I don't think that the article gave
any plausible evidence that it was a video chip bug.

I believe that the problem is that when printing characters on screen,
the KERNAL would first write the character and then set the color.  (I
haven't checked this, so this may be a wrong assumption.)  As the -01
KERNAL fills the screen with white spaces, the character to be printed
will very shortly flash as white before turning into the cursor color
(usually light blue).  This might be visible at the bottom of the screen
when scrolling a program listing.

Could someone confirm or disprove this theory?


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