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Establishing the Maximum Speed of a CD-ROM Drive

Posted by michael on from the science-at-its-finest dept.

UnknownSoldier writes "Ever wondered how fast CD-ROM drives can spin their CDs before the CD will self destruct due to centrifugal force? This person was too, and has his results. (So much for those 100x drives)."

4 of 489 comments (clear)

  1. Depends on the age of the CD by Taco+Cowboy · · Score: 5, Interesting



    Contrary to popular belief, plastic doesn't last forever.

    And since CD is made up of two layers of clear plastic, sandwitching a thin wafer of metal media inside, the more the CD is aged, the weaker the plastics of the CD become.

    And so, the maximum spinning speed for a CD depends on how old the CD is.

    I do have some pretty old CDs from the early 80's, and I will NOT put them in my 52X CDROM drive. Unless of course, I want to scrap bits and pieces out of my machine. :)

    --
    Muchas Gracias, Señor Edward Snowden !
  2. Why even spin the disk at all? by gnovos · · Score: 5, Interesting

    That is old technology, trying to mimic an LP and it needs to be changed!

    Instead of spinning the disk, just have one laser suspended above the CD with a splitter that alters the direction of the beam, like maybe similar in concept to a cathode ray beam. Have the "read" sensor at the focal point of a parabolic mirror covering the top of the cdrom case and fire the laser at whatever angle it takes to hit position X. The beam will bounce off the pit and either scatter or reflect back up into the mirror striking the focal point, with seek times limited only by the speed of light! Forget 100X, if you did it this way you'd be looking at 100,000,000x speeds from CDs that don't even move an inch!

    --
    "Your superior intellect is no match for our puny weapons!"
  3. Re:Who would want one? by mgv · · Score: 5, Interesting

    Who would want a 100x drive? I think I've sustained permenant hearing loss from the whine of my 32x drive.

    The biggest problem with these sort of drives is seek time. A modern drive can read the whole CD in under 2 minutes, but it will take a good fraction of a second to jump from one part of a drive to another. This doesn't improve alot no matter how fast you spin the CD.

    A far better solution would be to build a CD with a 640 MB Cache, and have it just read the whole thing into RAM.

    Given the price of RAM over the next few years, this sort of technology should available soon.

    Alternatively, it could be written into the OS itself. The only problem with this could be with some copy protection systems perhaps.

    Michael

    --
    There is no cryptographic solution to the problem where the intended receiver and the attacker are the same entity.
  4. A faster way (2,466x) by labradore · · Score: 5, Interesting

    This is a good way to get a fast CDROM drive:

    1. Buy a 10,000x10,000 dpi scanner with firewire interfeace
    2. Write cdrom image analysis algorithm.
    3. Scan cdrom image into temp hard drive space and analyse, extracting data

    This is based on these rough figures:

    • A cdrom is approximately ( PI*5^2 - PI*0.75^2 )= 76.75 sq. inches of data surface
    • If a cdrom has about 5.6 billion bits on that surface then the density is roughly 76 million bits per square inch.
    • That works out to about 8,800 bits per linear inch. Assume you will need a little better resolution than that because there is some empty space between the dots on a cd surface. 10,000dpi aught to be good enough.

    Assuming that the scanner is faster than the firewire (400Mbps) and 10% overhead for the data transfer, each cd image will be approx. 7.3 billion bits, taking just over 20 seconds to transfer. This device is a 2,466x speed CDROM "drive". Put that in your Pentium and smoke it! Scanner and algorithm design left as an excercise for the reader.