Below is a picture for the Brain Board. As I explained in my last post there was a common Brain Board that was used across the different variations of the development system.
Along the left side are the three serial connectors that provide the user interface to the system. At the bottom is 5 pin power connector and a three pin connector that goes to the reset switch on the front panel. At the top are two connector (on the back side of the board) that connect it to the Personality Board. There are spots for two pairs of connectors but only one pair is populated.
I have labeled the major chips on the board.
A. Four 2764, 8K EPROMS for a total of 32K or ROM.
B. Intel 8253 programmable interval timer.
C. Eight, 4164, 64Kx1 DRAM for a total ok 64K RAM.
D. National Semiconductor NSC800N CPU. This is National’s version of the Z80.
E. Three Signetics 2561 Programmable Communication Interface, one or each serial port.
F. This ZIF socket is for the EPROM programmers. There is a ribbon cable that connects it to the ZIF socket on the front panel. I am not sure why they spent the money for a ZIF connector on the inside.
Most of the rest of the board is 74 series logic and a couple PALs. There is one odd chip labeled 8188-U40. U40 is it’s location on the board so I assume it’s some sort of custom chip.It is near the EPROM programmer so might be part of that circuit.
