Re: System ROM 901227-01 wanted

From: Glenn Holmer (
Date: 2005-10-31 01:53:37

On Sunday 30 October 2005 14:26, Marko Mäkelä wrote:
> 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.

Is this what Brian Bagnall talks about in "On the Edge" (the new C= 
history book)? see p. 263, where they're talking about the first 
production run:

"The C64 seemed to have a congenital defect with the video chip. "You 
would see light blue sparkles on dark blue, especially after it heated 
up", says Bil Herd... "They rewrote the code so that the unused 
characters were changed to dark blue. It was sparkling dark blue on top 
of dark blue so you couldn't see it."

   Glenn Holmer (Linux registered user #16682)
   "Greater coherence cannot be achieved.  Not even the
    Netherlanders have managed this."  -Anton Webern

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