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

["Florin Iucha" <florin@iucha.net>]

Hello,

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.

When reading the same CD using the IDE DVD-ROM the time spent in system
is 5%. Also when the CD-RW is connected to the Advansys SCSI controller
the CPU usage is also negligible. The Adaptec-2920 uses IRQ 10 and does
not share it with any other board.

I notice an unusual number of interrupts in /proc/interrupts: after the
machine has been up for a couple of hours and I have written three CDs,
the statistics are:
          CPU0       
 0:     638458          XT-PIC  timer
 1:      15325          XT-PIC  keyboard
 2:          0          XT-PIC  cascade
 5:          0          XT-PIC  es1371
 8:          1          XT-PIC  rtc
 9:      17004          XT-PIC  usb-uhci
10:    3032143          XT-PIC  fdomain
11:      58021          XT-PIC  advansys
12:    2995779          XT-PIC  eth0
14:     107542          XT-PIC  ide0
15:       6895          XT-PIC  ide1

When loading the fdomain module I get:
   scsi1: <fdomain> No BIOS; using scsi id 7
   scsi1: <fdomain> TMC-36C70 (PCI bus) chip at 0xdc00 irq 10
   Bad boy: fdomain (at 0xd08b7866) called us without a dev_id!

Is there anything I can try?

Thanks,
florin

-- 

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

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