I tested two PCs that I had handy here in my office.  Using an ohmmeter
between 5 volts
 and the control lines with the PC off:

 a:  Compaq 486SX  has 4.7K pullups.
 b:  Clone 486 DX has 2.2 Meg resistance ( VLB I/O card).  Obviously in
this machine
 the "pullups" are actually MOSFET current sources internal to the I/O
chip.


In my experience, all PC standards are non-standard.  Last summer we
designed a device that interfaced
with the PC keyboard port which is also an open collector port.  We found
pullup resistors as small as
 470 ohms in one machine.  Most typical was 2.2K, several 1K pullups were
found.

 --- Steve

>Question is: What ARE the pullups, usually?

>According to the Parallel port-FAQ, the control ports are supposedly
>pulled up by 4.7k resistors, if I remember right. I decided to
>check this out on three PCs I had in my vicinity. This can be easily
done
>with the following procedure:

>1. In DOS, run DEBUG and give the following command:

   >o 37a 4

>This sets the four control pins 1, 14, 16, and 17 high. The address
>37a (hex) is the standard parallel port address. Replace with whatever
>is the address for your system.

>2. Use an ammeter to measure the current between GND (any pin 18-25)
>and pins 1, 14, 16, and 17, respectively.

>3. For a 4.7k pullup, this current should be about 1mA (=5V/4.7kOhm).

>The result was interesting. For each single computer, the current
>was the same over the pins, but there was an order of magnitude
>difference between computers:
 >       Old Toshiba notebook (5 years): 0.44 mA
 >       Medium old Taiwanese desktop (3 years): 6.1 mA
 >       New Taiwanese notebook (1 year): 1.0 mA