Having multiple drives with a parallel cable is possible if an and circuit is added to the /FLAG lines of the cables. The line is held high by the drive then cycled low when needed. When multiple drives are attached with parallel cables, the low signal doesn't get through because the other drive(s) are also holding the line high. By adding an AND circuit to the cable(s) the signal will get through (normal communication operation allows the computer to know which device is signaling.) On my real computer (currently not operational,) this is done with a User Port expander I have. It uses a T74LS11S1 chip for this function. This allows multiple devices (including Drive Parallel Cables,) to be used on the User Port at the same time. I imagine Expansion Port adapters with multiple connections (I've seen pictures, but have never actually owned one,) use a similar method.
This could have multiple applications outside of just parallel cables, I imagine. Enabling a User Port printer & User Port modem at the same time, for example.
