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Re: parallel port using lots of CPU



On Monday 20 September 2004 07:29 pm, Ross Boylan wrote:

> I'm not sure who *you* means, but my original thought was that the
> device driver associated with the port might be using a lot of CPU
> cycles.

I think that's exactly what's happening, and I was curious as to why
others thought that it wouldn't be.

> So the thing reported as parallel:/dev/lpt0 (or whatever it was) is
> actually part of CUPS?

Yep.  It it's most likely the kernel accumulating all of that CPU time,
but since CUPS is the application making the IO request, it gets the blame.

Is your parallel port running in DMA mode?  Mine is, based on dmesg:

    parport: PnPBIOS parport detected.
    parport0: PC-style at 0x378 (0x778), irq 7, dma 3 [PCSPP,TRISTATE,COMPAT,EPP,ECP,DMA]

If it's in a non-DMA mode, then I wouldn't be surprised to see the poor
performance you're describing.  Also, I'd strongly consider migrating to
using the USB interface if at all possible - it really is much faster
(and typically better-behaved) than parallel.
-- 
Kirk Strauser

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