ORDINATOR CPU extension board
The CPU extension board of the ORDINATOR contains a number of small
circuits that didn't conveniently fit on another board. This includes
two 4K EPROM chip sockets, a 8253 timer chip and an 8-bit DIL switch.
Although the board had two EPROM sockets, we used only one. It contains the DIAMOND extension. The timer chip supplies the 10 Hz
interrupt used by TS to switch processes. The DIL switch was used to set boot options for DIAMOND and TS (console baud rate, floppy boot enabled, TS boot enabled).
The ORDINATOR CPU extension board is also described on page 19 of the book "THE ORDINATOR PROJECT".