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Re: parallel port using lots of CPU



On Monday 20 September 2004 10:09 pm, Ross Boylan wrote:

> Mine says
> parport0: Printer, Lexmark International Lexmark Optra E310
> lp0: using parport0 (polling).
> parport0: PC-style at 0x378 [PCSPP]
>
> I don't really know what that means, but it apparently has no
> interrupts and there's no reference to DMA, just PCSPP.  Perhaps I can
> tweak my BIOS.  Unfortunately, my system is interrupt starved.

Yep, that's what it means.  What do you have contending for interrupts?

> The (polling) certainly suggests that I am, umh, polling.  Which would
> explain the CPU useage.  Would this also slow down how fast it takes
> to ship stuff out?  Printing graphics is painfully slow, e.g., 20
> minutes per page (with 300dpi!).

Absolutely!  I have an HP LaserJet 1200 hanging off a FreeBSD server.  When I 
was using CUPS to print large PostScript images, it could easily spend 20 
minutes pushing the data across.  DMA mode wasn't significantly faster - 
maybe 20% or so - but the CPU was mostly idle the whole time instead of 
pegged at 100%.  Switching to USB cut those times in half, but that would be 
even more pronounced if my printer didn't have a dog-slow engine.

> I was under the impression that USB was a bit experimental on Linux,
> but I did form that impression awhile ago.

I hope not!  That'd make my keyboard, mouse, Palm, and keychain drive stop 
working.  ;-)

> Partly as a result of that, and on a more mundane level, I don't have a USB
> cable, and I remember them costing more than a completely trivial amount. 

I'm sure you can get one for $5 or less.
-- 
Kirk Strauser

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