Q: Can I attach a math coprocessor?
Yes, the Rainbow can have an 8087 math coprocessor, but an expansion board is necessary. To install the 8087 daughterboard, you need to remove the memory expansion board and the hard drive controller if either is present. Then the 8088 CPU must be removed from its socket. No soldering should be required, since most Rainbow's 8088s sit in a chip socket. Next, plug the 8088 CPU into the CPU socket on the coprocessor board. The CPU socket is the one closest to the ribbon cable connector. Insert female female connector on the coprocessor daughterboard into the expansion port where the memory expansion card usually sits (between the hard drive expansion ports and the graphics expansion port). Finally, connect the ribbon cable (DEC part number 17-00662-01) to the 8088 CPU socket on the motherboard. If you have a hard drive controller, reconnect it to it's original expansion ports. I you have a memory expansion board, plug it into the connector atop the 8087 coprocessor board.