Editing Schematic 320135 (Complete, Board 320137) (section)

== What these sheets contain ==
* '''Sheet 1''' — the 6502 at UF3, both 6520 PIAs (UB8, UG8), the 6522 VIA (UA5), the three MC3446 IEEE-488 transceivers at UA7–UA9, the LM555 retrace timer, the cassette interface with its TIP29 motor drivers and 7.2 V zeners, and the keyboard matrix pull-ups. '''No regulator''' — the board takes +5 V and +9 V unregulated from elsewhere in the machine.
* '''Sheet 2, Memory Section''' — the ROM and RAM array for this assembly specifically, which is what distinguishes the four boards.
* '''Sheet 3, Video Logic''' — character generator, video timing and the display output.

Some circuits on sheets 2 and 3 are marked with an asterisk and annotated '''"all ckts marked * are for BC machine only"''' — the business-keyboard variant.