On 23/11/2017 10:05, Jim Lesurf wrote:
In article ,
Dave Plowman (News) wrote:

Then the extra speed to read a dodgy CD rather pointless?

Depends a bit on the speed in question. Running at, say, x4 speed should be
enough to allow a re-read or few given a buffer. But CDROM drives in
computers and ripping software may tend to try and read at far higher
speeds because they (I guess) take for granted that the user wants to rip a
disc ASAP.

At some point this extra speed becomes counter-productive - either leads to
so many more read errors requiring re-reads that the rate of reliable info
extraction maxes (or falls), or means loads of mechanical noise, or both.

Quite a lot of computer drives will slow down as they run retries, which
tends to indicate reading does get easier at low speed.

One of my CDs I found in a hedge. It plays perfectly.

The only time I've had a dodgy one was some sort of pressing problem.
The manufacturer sent me a replacement disc, and I sent them back the
old disc with a report from the CD tester we had at work. It wasn't a
speck of dust, it was all over it, and I assume they had lots.

Andy