lpt0 printer slows system response significantly

[Ian Smith]

On Wed, 1 Nov 2006 Anton Shterenlikht wrote:
 > On Wed, Nov 01, 2006 at 10:49:36AM -0500, Lowell Gilbert wrote:
 > >  * Change the printer port to polled mode.  ["lptcontrol -p"]
 > >    With this kind of hardware, it may even speed up your printing as well.
 > 
 > 	Thanks a lot, I think it does print a bit faster. But more
 > importantly I see virtually no performance degradation during
 > printing.
 > 
 > 	Perhaps a sentence on this should be added in section
 > 9.3.1.3 (Setting the Communication Mode for the Parallel Port) of
 > the user manual somewhere in the end of this pararaph:
 > 
 > 	The interrupt-driven method is usually somewhat
 > 	faster but uses up a precious IRQ line. Some newer
 > 	HP printers are claimed not to work correctly in
 > 	interrupt mode, apparently due to some (not yet
 > 	exactly understood) timing problem. These printers
 > 	need polled mode. You should use whichever one works.
 > 	Some printers will work in both modes, but are
 > 	painfully slow in interrupt mode.
 > 
 > and then add something like:
 > 
 > 	On slower machines using interrupt mode might cause
 > 	significant degradation of the overall system perfor-
 > 	mance due to the interrupt service using most of the
 > 	CPU time. On such machines changing to polled mode
 > 	will balance the CPU load as well as result in
 > 	faster printing.
 > 
 > 	Perhaps I should send a message to the documentation
 > list?
 > 
 > anton

I'm not sure if that's generally true for slower machines; you haven't
said (or I missed) what sort of printer you're using, what filters you
run via printcap, and such?  Not one covered by the existing para?

I have a 1500c, bit faster than your 1700 @300MHz, that has printed lots
of large files via gs without ever seeing any significant irq 7 load nor
any slowdown of the machine at all - albeit using a slow old printer. 

Not that I see any problem with your proposed addition.  Perhaps 'On
some slower machines running fast printers using interrupt mode ..' ? 

Cheers, Ian