Strange things happen when reading from

[Christoph Groth <cgroth@gmx.net>]

Hello all,

My box is a PC with an EPoX 8KTA2 and a Duron 700, a Matrox Millennium
II PCI and a Gravius Ultrasound PnP (ISA).  It is running Debian 2.2r2
(Kernel 2.2.17).

The IDE-Devices connected to it are:
hda: Traxdata CDRW2260+, ATAPI CDROM drive
hdb: TOSHIBA CD-ROM XM-6002B, ATAPI CDROM drive
hdc: IBM-DTLA-307030, ATA DISK drive
hdd: SAMSUNG WU32163A (2.16GB), ATA DISK drive

I am quite happy with this machine except for one thing:

Whenever the CD-drives are accessed in some way (reading, burning) at
least two strange effects happen:

1) Sound played at 44kHz becomes noisy and literally slows down.
   Sound played at 22kHz or less isn't affected.

2) When connected to an ISP with the 56k external serial modem,
   massive communication problems appear.  E.g. ping doesn't work (it
   simply ceases to produce any output).  As soon as the CD-ROM access
   stops, everything works again.

Surprisingly the problem doesn't occur with the HDDs, only with the
CD-ROM-drives.

I have tried changing the IDE-cable, exchanging master and slave,
changing the BIOS-settings but the problem is still there.  What else
can I do?

I've asked in comp.os.linux.hardware but apparently nobody could help
me.

Maybe changing the PIO-/DMA-Mode could help, but I don't know how to
set them for CD-ROM drives (hdparm is only for HDDs).

While booting the kernel says

    ide0: BM-DMA at 0xe000-0xe007, BIOS settings: hda:DMA, hdb:DMA
    ide1: BM-DMA at 0xe008-0xe00f, BIOS settings: hdc:DMA, hdd:DMA

Does this mean that my CD-drives are using DMA?  Changing the
PIO-/DMA-Mode in BIOS doesn't change anything.

Any help is greatly appreciated,

Christoph