Re: Adaptec-2920 eats too much cpu time when reading from the CD-ROM

Florin Iucha (florin@iucha.net)
Thu, 6 Dec 2001 07:51:26 -0600

On Thu, Dec 06, 2001 at 09:28:08AM +0000, Alan Cox wrote:
> > I have recently purchased a Plextor 12x CD-RW and I have attached it to
> > and Adaptec-2920 SCSI card. The card uses the "Future Domain Corp. TMC-18C30
> > [36C70]" chip.
> >
> > The problem I see: when reading from the CD-RW my system becomes very
> > unresponsive and top reveals 90-95% of the time is spent on "system".
> > My CPU is AMD K6-III/500MHz with 256 Mb RAM.
>
> I'd expect that. The 2920 is pretty old. It has no DMA channel and several
> processes it must perform are polled not interrupt driven.

There is one interesting thing about it: when I write a CD, I write at 12x
- that means 1800Kb/s, which is comparable with the reading speed of 2400Kb/s.
But when writing, the system CPU usage is about 30%.

What could make the controller eat so much time when reading but not when
writing?

Thanks,
florin

PS. The patch fixes the "bad boy" message.

-- 


"If it's not broken, let's fix it till it is."


41A9 2BDE 8E11 F1C5 87A6  03EE 34B3 E075 3B90 DFE4
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