On Thu, Aug 25, 2011 at 06:13:03PM +0200, Gerrit Heitsch wrote: >Hm, I own a 6569R3, some 6569R5 and some 8565R2. I don't notice any >difference in picture quality between the 6569-Revisions Configure your screen to black-and-white, and you should notice that the 6569R5 generates 9 luminance levels. Here is a simple test pattern: Hit ctrl-9 to enter reverse mode, then hit ctrl-1, space, ctrl-2, space, ..., ctrl-8, space, cbm-1, space, cbm-2, space, ..., cbm-8, space. >the 8565R2 seems to provide a slighty brighter picture. It also has the >'grey-dots-bug'. If you write to the background or border color >register (even if this doesn't change the contents) you get a grey dot >on the screen at the moment the register is written to. The intro for >Giana Sisters does show that quite nicely. Looks like a kind of 'snow >effect' if done right. This doesn't happen on a 6569. On some 8565-VICs >it goes away once the chip warms up. > >The bug is also present with TED and the VIC used in the C128. It >seems as if it got introduced with the switch to HMOS. Right, I can confirm this. I did not know that there was a HMOS VIC-II for the C64. Hmm, now I got another question: What was the mysterious "always set this bit to 0" in the VIC-II? Was it used in some early 6567 revision? I do not remember any effect when I set it on any of the 6567 or 6569 that I had. D016 53270 VIC Control Register 7-6 Unused 5 ALWAYS SET THIS BIT TO 0 ! 4 Multi-Color Mode: 1 = Enable (Text or Bit-Map) 3 Select 38/40 Column Text Display: 1 = 40 Cols 2-0 Smooth Scroll to X Pos This is not to be confused with the C128 VIC-IIe test mode bit in $d02f or $d030 that really does something. This would not be the first bit that has been disabled in a Commodore video chip. In the NTSC VIC-I, there is a bit for enabling interlace mode. It does not work in the PAL VIC-I. I wrote a test program for it: look for interlace.prg and interlace.tar.gz at http://zimmers.net/anonftp/pub/cbm/vic20/programming/. Best regards, Marko Message was sent through the cbm-hackers mailing listReceived on 2011-08-25 18:00:13
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