FC3 Samsung DVD-ROM issues

[mndar]

I am unable to use my Samsung DVD-ROM (SD-616Q) under FC3. Although I can boot from the FC3 CD1 and the Rescue CD, I cannot install from the CD. I get a error message sayiing 'No FC3 CD was found!'. I can install properly from my Samsung CD-Writer. Anyways I installed FC3 from the ISOs on my HDD. but even after that, I can't use my DVD-ROM under FC3.
Here is what happens. I put in a CD and give the command
mount /dev/hdc /media/cdrom
and thats it, it gets stuck there, although the system doesn't hang.

The line corresponding to my DVD-ROM drive in /etc/fstab is
/dev/hdc /media/cdrom auto pamconsole,ro,exec,noauto,managed 0 0

'cdrecord -scanbus' detects the drive correctly. The firmware is the latest one from Samsung.

1,0,0 100) 'SAMSUNG ' 'DVD-ROM SD-616Q ' 'F404' Removable CD-ROM

I am using the latest kernel (2.6.11.3) . It detects the DVD-ROM drive correctly while booting up, displaying the buffer size as 512KB. That is correct.
I also tried checking if DMA was enabled

[root@mndar ~]# hdparm -d /dev/hdc

/dev/hdc:
using_dma = 1 (on)


I can use the DVD-ROM very well under Windows XP. So, I guess there is nothing wrong with the drive.
I can use my Samsung CD-Writer (SW-252B) very well under FC3. Even cd recording goes well. So I am assuming there is nothing wrong with the system either.

Are there any settings I need to make. Some changes in the /etc/fstab file or something ??

[mndar]

I got it...i disabled DMA using
hdparm -d0 /dev/hdc
now everything works fine.
Is this some hardware problem i should be worried about or its just some kernel/software compatability issue ?

[Bob D.]

Take a look at "man hdparm". I'm not sure I understand it clearly, but perhaps you need to use the -X parameter along with d1? I may be off-base here...

I'm a bit beyond my knowledge base, so perhaps a more skilled user will jump in with the answer.

Bob

[mndar]

Thanks Bob, I think i will be able to get my drive working with DMA, after i understand what all the manual says for 'hdparm'

-X     Set  the IDE transfer mode for newer (E)IDE/ATA drives.  This is
              typically used in combination with -d1 when enabling DMA to/from
              a drive on a supported interface chipset, where -X mdma2 is used
              to select multiword DMA mode2 transfers and -X sdma1 is used  to
              select  simple mode 1 DMA transfers.  With systems which support
              UltraDMA burst timings, -X udma2  is  used  to  select  UltraDMA
              mode2 transfers (you’ll need to prepare the chipset for UltraDMA
              beforehand).  Apart from that, use of this flag is seldom neces-
              sary  since  most/all modern IDE drives default to their fastest
              PIO transfer mode at power-on.  Fiddling with this can  be  both
              needless  and risky.  On drives which support alternate transfer
              modes, -X can be used to switch the  mode  of  the  drive  only.
              Prior to changing the transfer mode, the IDE interface should be
              jumpered or programmed (see -p flag) for the new mode setting to
              prevent  loss  and/or corruption of data.  Use this with extreme
              caution!  For the PIO (Programmed Input/Output)  transfer  modes
              used  by Linux, this value is simply the desired PIO mode number
              plus 8.  Thus, a value of 09 sets  PIO  mode1,  10  enables  PIO
              mode2,  and  11  selects  PIO  mode3.   Setting  00 restores the
              drive’s "default" PIO mode, and 01 disables IORDY.   For  multi-
              word DMA, the value used is the desired DMA mode number plus 32.
              for UltraDMA, the value is the desired UltraDMA mode number plus
              64.

It says "Use this with extreme caution! " , so I am a bit reluctant to try it out until I fully understand what it means!
Perphaps someone here could explain to me what it means. What is PIO, UltraDMA and why the hell my drive won't work if DMA is enabled? How do I disable DMA for the drive from the BIOS itself, if that is possible ?. Presently I have added the following line to my rc.local file, so that every time I boot, DMA is disabled for my DVD-ROM drive.
"hdparm -d0 /dev/hdc"