Subject: Parallel port CPU hog (was: Disk driver related problems?)
To: Mark White <>
From: Richard Rauch <>
List: port-i386
Date: 11/20/2000 22:38:19
You mention that accessing the parallel port causes CPU strain (oddly you
mention this under ``DMA problems''; as Manuel said, I don't think that
NetBSD provides DMA to the parallel port).

I've seen this, too.  Any heavy I/O will bring either of my two
NetBSD/i386 machines to their knees.  Other people have also reported
this.  (My suspicion is that it's just the basic overhead of doing an
interrupt for every byte sent out.  But there is no DMA option...and I
assume that if the parallel port had a hardware data buffer, /dev/lpt0
would actually use it.  If I were a hardware type of guy, I might verify
that last assumption; as-is, I don't know if a buffer is there, nor do I
know what would have to be done in order to use one in the driver.)

There is one solution that's been reported elsewhere, at least if you're
using a printer: Get a USB<->parallel converter and hook it up to a USB
port on your computer.  This, of course, assumes that you have, or can
get, a USB port in your computer.  (^&

(I assume that this works for more than just printers, but the person
commenting on this was using it for a printer.  I almost got one for
myself, but I really don't do that much printing.)

  "I probably don't know what I'm talking about."