|The other is the "SuperIO" parallel port that is built into the motherboard.
|It can only source 1.2-1.5 mA per pin.  I have driven a 12C508 (which
|requires 2 mA running at 4 MHz using the internal oscillator) from this port
|by using the "-SLCT IN" and "-AUTO FD XT" connected through diodes (to
|prevent backdriving).

I thought it was common for the non-data wires to be open-collector
with moderate pullips; using them for supplying power would seem
like it wouldn't be terribly effective.  Have you measured the data
pins?  Those should be beefier.

BTW, on the original PC printer port, all of the outputs except for
the eight data pins could be used as open-collector I/O pins, there-
by allowing full eight-bit transfer of data into the PIC.  Unfortun-
ately, Toshiba laptops (at least the ones I've seen) don't preserve
this ability.