PCB has a PLD, 74LS245 buffer for other half of data bus, and two IDE-connectors. Also there is a place for I2C-serial EEPROM.
7407 is fitted on the board to make a fast, high current sinking buffer. The CPLD can make a 37.300 or newer ROM to think it has the A600 IDE interface, and thus autoboots. ABEL sourcecode, no warranty.
If the 86-pin connector looks unusual, it's because I use it on a modified A500 system built in a IBM PC 750 desktop case.