I am not sure whether it is a cdrtools or kernel problem. I just noticed
using this command:

/usr/bin/readcd -v dev=/dev/hdc f=image.img -clone retries=128

leads to 100% CPU usage (depending on read speed). Writing this image is
no problem though (in high-speed). DMA is activated and using cdrdao CPU
usage stays low on reading the image. Leaving out the option -clone
option CPU usage stays low, as well. So is reading subchannels a
problem? But AFAIk cdrdao is configured to read subchannels, as well,
but doesn't show this problem (but I don't know whether it only reads
audio subchannels, though).

Anybody else making this observation?

bye,

Prakash