Kenbak-1 Motherboard

Copyright 2007 by John Blankenbaker

The logic board, also called the mother board, held the integrated circuits which were soldered into place. This was a two-sided board designed by very conservative standards. The view above is the “top” side on which the components were mounted. (Compare to the interior views shown elsewhere here.)

The large silver-colored areas in the view are power (+5v) and ground runs. The logic inputs and outputs of the integrated circuits and other components were connected by 50 mil width etch paths. As a further note of the conservative design, no paths were run between the pins of the integrated circuits. On the lower or opposite side of the board, the signal paths tended to run horizontally in the opposite direction.

The area on the right above (the right 40%) held the “state” logic. There were 32 states (not all used) and each state was assigned a specific task such as locating the next instruction. Logic determined the next state. The logic for processing was located in the center and on the left were the memory and timing circuits. Input and output were along the lower part in the view.

 

Mother Board

This view shows the mother board with the components mounted on it. The power supply has been laid back and the front panel has been tilted forward. This was the position when the computer was opened up for serious work.  The smaller black rectangles, about 130 of them, are the ICs. The red objects are capacitors.