PET/CBM System Boards There are four major versions of system board for the PET series. Each has significant functional differences. New system boards were not always introduced the same time as new computer models. Also, newer system boards were used to repair older computers. As a result, the label on the outside of the computer does not necessarily indicate the system board inside. Static Board (PET 2001) Four variations based on type of RAM(6550 or 2114) and ROM(6540 or 2316B). 4K or 8K static RAM (selected by jumper). 40 column display A video interrupt interferes with disk drive operation. Display timing not compatible with Basic 4.0. ROM sockets: A2 2K character ROM sockets: A2 2K character (2316B) H1 C000-CFFF (6540) H1 C000-C7FF H2 D000-DFFF H2 D000-D7FF H3 E000-E7FF H3 E000-E7FF H4 F000-FFFF H4 F000-F7FF H5 C000-CFFF H5 C800-CFFF H6 D000-DFFF H6 D800-DFFF H7 F000-FFFF H7 F800-FFFF Dynamic Board (PET/CBM 2001-N/2001-B/4000) 4K, 8K, 16K or 32K dynamic RAM (selected by jumper). 40 column display Can run all versions of 40 column Basic (Basic 1 must be copied to 4K ROMs) Can be jumpered to replace the older board. ROM sockets: UD3 9000-9FFF UD4 A000-AFFF UD5 B000-BFFF UD6 C000-CFFF UD7 D000-DFFF UD8 E000-E7FF UD9 F000-FFFF UF10 2K character 80 Column Board (CBM 8000) 16K or 32K RAM (selected by jumper). Uses CTRC to generate 80 column display. Can only run the 80 column version of Basic 4.0. Not compatible with older boards. ROM sockets: UA3 2K or 4K character UD6 F000-FFFF UD7 E000-E7FF UD8 D000-DFFF UD9 C000-CFFF UD10 B000-BFFF UD11 A000-AFFF UD12 9000-9FFF Universal Board (CBM 8000/PET 4000-12) This is an 80 column board with jumpers for different configurations. 16K or 32K RAM (selected by jumper). Uses CTRC to generate 40 or 80 column display (selected by jumpers). Can only run Basic 4.0 versions that support the CRTC. Can be jumpered to replace all older boards. ROM sockets: UA3 2K or 4K character UD6 F000-FFFF UD7 E000-E7FF UD8 D000-DFFF UD9 C000-CFFF UD10 B000-BFFF UD11 A000-AFFF UD12 9000-9FFF