another superdrive question

Discussion in 'MacBook Pro' started by brentg33, Jan 13, 2010.

  1. brentg33 macrumors 6502a

    Joined:
    Mar 5, 2007
    #1
    ok, so a few days ago i took my 2 1.2 year old MBP to the genius bar and had the superdrive replaced. So today is the first day i am trying to burn a .iso to dvd. I am using toast and initally it started at 6x i believe. about 1/2 way through burning is slowed to a crawl to about 2x or 3x. .... is this normal? the iso was stored on my external HD connected via FW800. It seems to have burned a working disc however.

    thanks
     
  2. NewMacbookPlz macrumors 68040

    NewMacbookPlz

    Joined:
    Sep 28, 2008
    #2
    I wouldn't call it normal, but I have had that happen before while burning a DVD+R disc...only 1 out of 10-12 I've recently burned. Maybe it's the drive auto-sensing the disc speed as it can when you insert the disc, and slowing down due to something with the optical material as the disc goes?
     
  3. spinnerlys Guest

    spinnerlys

    Joined:
    Sep 7, 2008
    Location:
    forlod bygningen
    #3
    The speed has to get slower, as the burning process begins at the beginning of a disc, which is nearest to the CD/DVD. As the burning process progress the laser has to move away from the center. If the superdrive would burn the outer regions of CD/DVD with the same (faster) speed as the inner region, the spinning could cause damage.
     
  4. NewMacbookPlz macrumors 68040

    NewMacbookPlz

    Joined:
    Sep 28, 2008
    #4
    I thought it was the opposite. The disc rotational speed is fixed at whatever #x value. As you reach the outside of the disc, that portion is moving faster rotationally and in more data is written in a given amount of time.
     
  5. spinnerlys Guest

    spinnerlys

    Joined:
    Sep 7, 2008
    Location:
    forlod bygningen
    #5
    You might be right.

    It's late and I myself find it confusing right now. Will check back later.


    But to that slower burning issue, I have experienced the same with many DVD writers in Mac Pros or iMacs or MB(P)s.


    EDIT:
    DVDs hold seven times more information and spin three times faster than a CD. The rotational speed, or angular velocity, of a DVD goes between 570-1600 rpm (rotations per minute). The closer to the center of the disc, the faster it spins and which is why there is a range for the angular velocity and not one specific number. This means the "read head" passes the same length at all times and radii. Theconstant linear velocity (CLV) is why a DVD spins slower on the outer edge and faster on the inner edge.

    from http://hypertextbook.com/facts/2003/ClerbieMontilus.shtml

    or

    DVD players also usually read discs at a constant linear rate. The disc's rotational speed varies from 1530 r/min (actually 25.5 Hz), when reading at the innermost edge, and 630 r/min (actually 10.5 Hz) at the outer edge.[1] DVD drives’ speeds are usually given in multiples of this figure.

    from http://en.wikipedia.org/wiki/Revolutions_per_minute
     

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