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Re: parallel port using lots of CPU

Parallel ports generate an interrupt (and so a context switch) for every byte that goes out, the hardware provides no buffering as serial ports do (and for some reason, the industry never saw the need).

In NT/XP, MS supports parallel ports grudgingly and encourage you to invest in a USB device. I imagine it's the same for Linux.

Your printer appears to support USB, why not give it a whirl?


----- Original Message ----- From: "Ross Boylan" <RossBoylan@stanfordalumni.org>
To: <debian-user@lists.debian.org>
Cc: "Ross Boylan" <RossBoylan@stanfordalumni.org>
Sent: Monday, September 20, 2004 13:58
Subject: parallel port using lots of CPU

When I print graphics my parallel port consumes all available CPU.
Admittedly the jobs are large (40-90MG), but it seems odd so much
attention is required.  Is something wrong, or do I just have to live
with it?

2.4.26 kernel on Athlon CPU.
Lexmark Optra E310 is the printer; it speaks postscript natively.
Gigabyte GA-7IXE4 motherboard; the parallel port is on the board.

Originally I was using lpd in the lpr package.  With that, lpd showed
as the CPU consumer.  I just switched to CUPS; now parallel:/dev/lp0
shows as the CPU consumer.  My guess is that it was before, but the
time was just being attributed to lpd.

P.S. Maybe it is a hardware limitation; under Windows NT the parallel
got a kind of odd treatment, including the fact that the driver had to
poll it and some utilities couldn't use it, though they could under
Win95.  I always thought it was just an NT quirk.

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