My Dell XPS17 has been running OK with 16.04 and has recently done the upgrade to 18.04.2. The CD/DVD drive worked fine on 16.04 to the extent that this was the device of choice for recording and copying CDs and DVDs. But on 18.04 It records CDs/DVDs OK and reads DVDs, but is glacially slow when reading CDs.

CD-Rs and DVD-Rs record at around 2-3MB/s and 3-4MB/s respectively but I noticed that Brasero was taking a longer to compute the checksum for CDs than for DVDs. Doing a test, I found reading back a CD-R takes about 19 minutes for 710MB at 600KB/s, while the same CD took less than 5 mins to record. Using an external Dell USB2 CD/DVD reader the same disc reads in 4 mins at 1.5MB/s. On the other hand Recording and reading back DVDs seems to be OK with a read speed of around 4.7MB/s.

There's a Win10 system on the same box and I found that the DVD performance was much the same as with Linux, while the CD read speed began at 600KB/s quickly building to 2.5MB/s and completing the operation in around 4 mins for 710MB.

I've tried to look at the settings and as far as I can tell DMA is enabled so I'm a bit foxed.

The optical drive is a Toshiba Samsung 12.7T SATA DVD+/-RW 8X and the CPU is a series 2 core-i7 with 8GB memory and 2 x 500GB HDDs with plenty of space.

It appears to be a CD read problem. It doesn't matter where or how the CD was cut, Windows, MAC, Ubuntu, or commercial ROM. Doing some more tests I discovered the problem arises when I move to 18.04.2 either via the upgrade process or a clean out-of-the-box install, the only customisation being to add seconds to the panel clock. Thunar takes 20 mins (5 times as long as on 16.04) to copy a 710MB test CD but only 4mins 20 secs for a 2GB DVD at 6 -> 8MB/s.

I'd appreciate any help or pointers as to how I might solve this issue.

Tks in anticipation