> I tested this config (Ultra-DMA mode 2 drive + DMA mode 2 CD on the same
> channel on a PIIX4), it worked for me ... but IDE appears to be quite
> sensitive to various electrical parameters.
> Did you try to disable DMA for the CD in your kernel config file ?
> A line like:
> cd*     at atapibus? drive ? flags 0x0ff0
> should do it.

Yes, PIO 4 works, but it sucks too much CPU time
(32Max CDROM -> 45% of Pentium II/400Mhz). I am going to try other drives
next week, maybe my drive or cable is defective.

> > 2) disk access is stuck on after bootup, but "missing interrupt" error
> >    had unwedged it for me
> 
> "Disk access led" :)
> Well, it happens for me too with some ATAPI devices ... I didn't find a
> solution yet.

Something is not initialized on startup but is reinitialized after error.

BTW, cd driver does not properly check request size when reading
     through the end of partition, dd if=/dev/rcd0a of=/dev/null bs=64k
     results in 

cd0(pciide0:1:1):  Check Condition on CDB: 0x28 00 00 04 d6 00 00 00 20 00
    SENSE KEY:  Illegal Request
     ASC/ASCQ:  Logical Block Address Out of Range


-- 
Zdenek Salvet                                              salvet@ics.muni.cz 
Ustav vypocetni techniky Masarykovy univerzity, Brno
tel.: ++420-5-41 512 257                           Fax: ++420-5-41 212 747
----------------------------------------------------------------------------
           If God had meant for us to be in the Army,
         we would have been born with green, baggy skin.