Re: Detect a C128 from C64 mode

From: Marko Mäkelä (
Date: 2003-02-14 18:14:07

On Fri, Feb 14, 2003 at 04:34:09PM -0000, Christopher Phillips wrote:
> How common is the IIe?  I'm not familiar with the revision nomenclature.

As common as the Commodore 128, 128D, 128DCR and 128CR.  VIC-I is the common
name of the audio/video chip in the VIC-20, VC-20 and VIC-1001.  The video
chip in Commodore 64, UltiMax, SX-64, 64c and 64G are called VIC-II.  Of
each chip, there exist at least two different versions (PAL and NTSC) and
usually several revisions.

> this reminds me of the TEST bit on the vicIIe.  You can detect a vicIIe by
> reading the raster, setting the test bit for a few cycles, and checking the
> raster again.  Anyone unfamiliar with this may want to check the 60hz trick
> regarding this bit.  It seems while the test bit is set, the vicIIe advances
> one raster per 1mhz cycle(!). ;)

Yes, that was why I said why I wouldn't use the test bit.  If you dig up
older discussions on this list, you might see a reference to a program
that displays an interlaced on the C128 by abusing the test bit to generate
odd and even frames.  A similar effect could be achieved on the plus/4 by
writing the horizontal raster register if I remember correctly (Levente,
are you listening? :-)), but it might not work on some TVs.

While we are at this, has anyone been able to produce a proper Ceefax
(teletext, Bildschirmtext, text-TV) signal with a Commodore computer?
None of the TVs or monitors I have access to is equipped with a Ceefax
decoder, so I have an excuse for not having tried it. :-)


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