Setting (U) DMA
To set DMA mode, the following command is used, the command itself can be used but a combination of –X is preferred to ensure that the drive itself is programmed. Read the drive documentation before trying this.
hdparm -d1 /dev/hda
hdparm -d1 –X mdma2 /dev/hda //setting xfermode (multiword DMA Mode 2)
- X sdma1 is used to set simple mode DMA transfer
- -X mdma2 is used to set multiword DMA mode 2
- -X udma2 is used to set ultra DMA mode 2 transfer (you need to prepare the chipset first)
Note. The –X is used to set transfer mode for newer drive (E)IDE use it only when the chipset supports it. Query the setting first before you make changes. New drives may already turn on this PIO modes at power on.
Always query and benchmark the drive after your settings, to ensure that the drive has been programmed the way you want it.
Note. All modifications or setting are not saved permanently. If you reboot the system, the settings are lost. So when you do this make note of the settings, create a file and execute it via bash script, or via /etc/rc.d/ alternatively and probably best, add the line in your /etc/rc.d/rc.local
All CD-ROMs, CD Writers, DVDs and IDE ZIPs drives are treated as SCSI devices under Linux. Most CD-ROMs are detected automatically, especially if you are installing Linux from CD-ROMs, when you finish the installation the Drive should be already working.
Make note that even the CD-ROM is configured properly; it may not be available when you need it. A CD-ROM, in order to be accessible needs to be mounted.
To find out about the real name of your device type this:
- ls -l /dev/cdrom
- dmesg | grep CD
To mount the CD-ROM, use these commands:
- mount /dev/cdrom /mnt/cdrom
- mount /dev/scd0 /mnt/cdrom
- mount /dev/scd1 /mnt/cdrom
- mount /dev/hdb /mnt/cdrom
Where /mnt/cdrom is a directory to temporarily, read the information contained in your physical CD-ROM. /dev/xxx is your physical device.
Some times you need to eject a CD from the CD-ROM drive, but the drive won't open, it is because it is mounted. In order to remove the CD you have to un-mount the drive first. To un-mount the drive, use this:
Note. Mount and umount is executed as root.