> I think the choice of the IBM printer port were determined by costs.
> I just checked the PC (not XT) reference manual, and the mochrome/
> printer adapter card uses a single 7405 for all the device control lines.
> These lines come from a latch which is cleared by master reset.
> Might have cost another chip to change it.
>
> A more interesting question is why the port was not made bidirectional.
> All the gates are there, and if an unused latched output had been
> connected to the output enable on the driver -- a no-cost change --
> we would have had an 8 bit bidirectional port with control lines.  Slow
> (because of the caps on the data lines) but much better than what
> we have been stuck with since then.

Actually, if the control lines are used bidirectionally the current printer
port design really isn't all that bad; in fact, in some cases it may be
better to use the port as two eight-bit paths and one control line than to
use the data bits bidirectionally.  Unfortunately, the control signals are
not bidirectional on the Toshiba Satellites and I'm a bit concerned about
whether they may have that problem on other machines as well.