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This is a 40/80 column switcher for Commodore PET Universal Dynamic PET motherboards. These motherboards could be configured as either 40 column or 80 column depending on the settings of several jumpers on the board. The Comspec 40/80 switcher board allowed you to switch to either mode with a single toggle switch. The switch must be changed while the PET is turned off. The switch also selects the appropriate Editor ROM to handle 40 or 80 columns.
My goal is to reverse engineer this board and then modify it to work via software. Thanks go to Leif Bloomquist for the loan of the PET with the switcher installed.
The board is connected to the PET motherboard overtop the 40/80 configuration jumpers as well as several additional points on the board. Infact it is necessary to cut some IC pins. Refer to the connection and wiring diagram below.
I have photographed the board and created connection and wiring diagrams. I now have a project to clone this board. Please check it out here!
Page Created: Oct 02/2014. Last updated: Sept 14/2017, 9:15pm EST
Send comments or feedback to Steve Gray(sjgray@rogers.com)