CD data recovery?

[Lennart Sorensen]

On Tue, Sep 21, 2004 at 06:45:37AM -0400, James Knott wrote:
> And, due to CD layout, only full disks will ever use that 50X space, 
> though you could always pad the disk, so that the data is at the outside.

I believe dreamcast games took advantage of that and padded out their
games so the data was as far out on the disk as possible (they were also
modified CD format holding about 1GB, but same layout otherwise).

> Incidentally, I believe you mean linear rate, not rotational.  If 
> rotational, the outer tracks would be spinning faster or slower (RPMs) 
> than the inner tracks.  That would definitely cause the disks to 
> fracture, no matter how fast they were spinning.  ;-)

Well the read speed is a function of where on the disk the head is
pointing and how fast the disc is rotating.  Since the data is stored at
a constant bits per distance of track, there is more data on one
revolution on the outside than the inside, hence at a constant rpm you
get higher read speeds at the outside than the inside.  original CD
drives up to around 8x were constant linear speed, so they changed
rotation speed as they went along to keep a constant read speed, while
new drives use constant rotation speeds instead and have varying read
speeds as a result.

As far as I remember my 52x CD writer will only read pressed CDs at up
to 40 or 48x (probably 40x) to avoid damaging them, while cd-r it will
run at 52x.  Supposedly they are more durable than pressed discs.  The
drive is also supposed to have a reinforced front bezel, just in case :)
I don't want to know what the inside of the drive would look like if it
ever had a need to using that reinforcement.

Lennart Sorensen
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