The Rate Generator board is a separate board that is directly connected to the PC-32 board's I/O port. It's design can be seen below. (click on the image to see the graphic at larger size (2.3 MB)) :
Dimensions are 10 mils (.010 inches) for the tracks (dark spaces) in the copper. The smallest pads for the large processor chips (square array of 80 pins, 20 on a side) are spaced 25.6 mills (0.65 mm). In the blown up image, you can see the "foot" which holds the mill bit at the correct depth, it appears as a "ghost" image to the tracks.
rosing@neurophys.wisc.edu.