Slow read and write speeds from ATAPI (CD / DVD) devices

If you are experiencing speed issues with your CD or DVD drive, here are some tips that might help:

1. Make sure that you use an 80-conductor data cable and that it is fine.
2. Ensure that DMA is enabled for your drive. If you use something like K3b, opening it will pop up an error stating that DMA is not enabled and the fix for it. However, Linux should have it enabled by default. If it isn't, you very likely have a cable related issue as noted in 1.
3. If your cable is fine and DMA is still not enabled, you might need to enable it manually. The application to use for this purpose is hdparm.
   • On the command-line, type sudo hdparm -d /dev/hdX where hdX is the drive in question. This should state if DMA is currently enabled or not.
   • Next, run sudo hdparm -tT /dev/hdc a few times and note down the results. This benchmarks your drive's performance and you will be able to use these results to gauge if there have been any improvements later on. You will need to insert a filled DVD / CD for this test.
   • Finally, run sudo hdparm -d1 /dev/hdX to enable DMA. Perform the benchmark once again, to see if there's been any improvement.
   • If, even after enabling DMA, it is switched off during the next boot, you will need to add the hdparm command into a config file that is run during boot-up.
4. FYI: Typical transfer speeds on a 16x DVD-ROM drive will be around 15MBps - 22MBps. Anything consistently slower indicates performance issues.

Hope this helps somebody :)