How do I diagnose parallel port problems?

[genterminl]

I just got a new printer and spent all day getting strange errors (PCL XL error) no matter what driver I used. In desperation, I switched the printer to USB and it works fine with the recommended driver. I had previously had similar problems with an older printer. I have a strong feeling that the parallel port is garbling communications. Is there any reasonable way to diagnose this?

I have parport, parport-lp, and lp modules installed. It did not matter whether I configured it so it ran polling or interrupt driven - same behavior. It's no longer critical, since the printer works, but now I'm curious.

Thanks for any hints or pointerrs.

[slashdevslashtty]

I'd guess some BIOS tweaking may be able to fix this.