[SGVLUG] off topic - hardware question

[Emerson, Tom]

> -----Original Message-----
> Behalf Of Steve Bibayoff
> 
> On 1/26/06, jmd <jmd8800 at charter.net> wrote:
> 
> > my question is what causes the cdrom/dvdrom drive to reach these
> > speeds. there must be something that causes this to happen so
> > frequently.
> 
> Not sure how this is a related to Linux in any way, but

it could be a driver issue -- and in this case, Linux can end up "smelling like a rose" if played right...
 
> > the particulars:
> >
> > [...] the DVD RW drives were (2) AOPEN (forget speeds ...
> > but they were fastest available in the last 6 months).
> > the sony is a DVD +/- R dual layer.

A quick google search of "exploding CD" shows several sites that have done the "mythbuster" thing of rigging up something to spin disks and note when they fail.  One guy used a hand-held dremel, another guy had something that looked like a bench grinder.  Both reported that somewhere around 25,000+ RPM the disks would fail catastrophically (one guy reported fragments of the disks went THRU a 1mm alumimum guard installed specifically to stop said fragments)  Drives in the 50+ range need to spin the disk somewhere close to this, so this is not unusual.  Drives that are insanely faster than this are actually OK -- they use multiple read-heads so they can spin slower yet get higher throughput.

[this was the better "mythbuster" approach, complete with an attempt to strengthen a CD using kevlar: http://www.paintbug.com/cdexplode/  He notes that a 52x "CLV" drive would hit 27,000+ to read the innermost tracks, while a 64x would exceed 32,000]

> I've seen this happen when you try to make a copy of any type of cd
> from Microsoft using MS Windows. Usually the drives where close to
> toast afterward.

Ahhh -- what an easy conspiracy theory to put forth: MS knows disks have problems at high speed, and as they control the driver and copying software, it would be a simple matter to "recognize" that a MS disk is being copied and therefore spin the disk outside of "spec" during the copy...

Which of course brings me to my point above about Linux -- how often do you /really/ need 50+ read speeds?  Most of the disks I use are installation disks, and are read once to copy the program to the hard drive.  Since I'm in a "take my time" frame of mind anyway, a slower read speed isn't going to upset me -- 8x should be fine, and if there is "too much" data to consider reading at 8x, it should be on a DVD anyway (which already reads faster to begin with -- roughly 9x according to one site I checked)

In any case, with access to the driver code, it would (should?) be a simple matter to put a "speed limit" in to ensure the disk is never rotated faster than, say, 15,000 rpm...