On Fri, 2 Oct 2009, Ethan Dicks wrote: > Well if there were display frequency changes between the 1977 PET and > the 1978 PET, then I can entirely understand what I'm seeing on the > display. Obviously there were changes between the 4032 and the 8032. > I had no idea there were changes between 40col boards. Some 40 col. PETs work at the same frequency as the 8032, usually 12 inch displays, but also a few 9 inch ones. The determining factor is the 6545 CRTC chip. The frequency is determined by how the 6545 is programmed. It can be programmed to run at the frequency of the older PETs. If you are placing a board that does not use a 6545 in a PET that also does not use the 6545, then the frequency should be the same. In this case, the symptoms you describe indicate a defective timing circuit for the video horizontal and vertical drive lines. Also, these lines depend on the 5V power supply. If this is low, it can also cause these symptoms. wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2009-10-06 07:00:10
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