Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!uokmax!occrsh!fang!alfred!tous!tarpit!bilver!bill From: bill@bilver.uucp (Bill Vermillion) Newsgroups: comp.arch Subject: Re: CD-ROM documents (was Paperless Office) Message-ID: <1990Dec8.173257.2115@bilver.uucp> Date: 8 Dec 90 17:32:57 GMT References: Reply-To: bill@bilver.UUCP (Bill Vermillion) Organization: W. J. Vermillion - Winter Park, FL Lines: 32 In article aglew@crhc.uiuc.edu (Andy Glew) writes: >>> Why are CD-ROM seeks so slow? Is it related to the spiral tracking? >> >>The audio Compact Disk spec includes constant linear speed along the >>spiral track that runs the entire length of the disk. The average >>seek includes moving a significant distance along the radius of the >>disk, requiring a noticable change in the rotational speed of the >>disk. That average change in rotational speed is the critical path >>factor in the half second seek time. > >Seems to me that the same techniques that are used to get constant >linear density (as opposed to constant angualr density) on regular >disks should apply. Key word in your description is density, while in the cd-rom it is velocity. In changing density you don't have to change the angular velocity of the disk, you change the rate of data flow. You keep the disc speed the same. In the cd-roms you keep the data flow the same, and increase the density by changing the rotational rate. To change the cd-roms to another format would break the CD specs and you would have to have specialized data drives, and not be able to take advantage of the much larger manufacturing quantity cost economies. -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP