The RA1792
Page 9
The Processor Board

It goes without saying that the history of the Processor Board is colourful. Note the four different styles pictured below … and I wouldn’t rule out there being others out there.

Early pre-BITE, 3 x EPROM, 2 x RAM, old-style battery, 1982?
2 x EPROM, 2 x RAM, old-style battery, 1988?
2 x EPROM, 2 x RAM, new-style battery, 1989?
2 x EPROM, 1 x RAM, new-style battery, 1989?
The Processor board in my RA1792
Same as ‘top right’ but with new battery on daughter board.
Firmware appears to be ‘special’ X82121

The chosen microprocessor for the RA1792 was the Fairchild F8 or 3850 and like most processors of its time, additional interface chips were required. Thus a 3853 Static Memory Interface (SMI) chip is mounted alongside. Depending on board version, the firmware is located on either 3 x 2716 or 2 x 2732 EPROMs with either 1 x TC5517 or 2 x D445LC as non-volatile RAM. CPU clock speed is an eye-watering 2MHz!