Reply 20 of 578, by CodeKiller
Based on some info here (jumpers), datasheets of ICs, pc hardware book (joy port) and mainly based on some pictures of the card, I have further reversed it. The joystick port is fully traced, but the 6581 /CS, the 74ls245 /oe and the ISA bus 'i/o ch rdy' lines are still not known.
However the clock divider isn't what you expected: the first stage (74ls192) resets to 2 after counted 9 (upwards) - making it a 1/8 divider, and then it drives a 1/2 counter to make a 50% square wave. (effectively making it 1/16 divider)