When I installed OS/2 on my PC and tried to print to the same printer that worked fine under DOS and Windows, the printer produced one character and stopped, and OS/2 subsequently informed me that the printer was offline or out of paper. Most of the information available for dealing with this problem deals with IRQ conflicts, bi-directional parallel ports, cable length, etc. However, I found that in my case the problem could be eliminated by bypassing the automatic parallel printer switch I use to share one printer among four PCs.

I contacted the company that marketed the switch I was using, as well as several other printer-switch vendors, and found them to be completely unaware of any OS/2 compatibility issues. IBM Tech Support gave me the too-general answer that you could not use an automatic parallel printer switch with OS/2. Finally I happened across an ad from Western Telematic (1-800-854-7226) which claimed OS/2 compatibility for their printer switches. Based on my own experience and on information from Western Telematic, the issues are as follows:

In terms of OS/2 compatibility, there are two types of automatic parallel printer switches: polling devices and simultaneous-input devices.

Generally, the less-expensive ($50 to $150), commonly-available switches are polling devices. They check each input port in turn, and when input is detected, they accept input from that port only, blocking out the other ports until the print job is completed. This is the type of switch I was using, and it would not print even if I was the only user trying to print.

Simultaneous-input devices are more expensive. These switches accept simultaneous input on all ports, storing the data in a built-in buffer until the printer is available. Western Telematic indicates that their switches, which use this technology, are OS/2-compatible.

In my case, since only one of my four PCs is running OS/2, I found a less-expensive solution: I installed a parallel printer buffer device between my OS/2 PC and the printer switch. This eliminated the problem, even if the printer is in use by another PC.

Ken Reeder
74670,1563