Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!wuarchive!zaphod.mps.ohio-state.edu!usc!ucsd!hub.ucsb.edu!6600dan From: 6600dan@ucsbuxa.ucsb.edu (Dan Zerkle) Newsgroups: comp.sys.amiga.hardware Subject: Re: Can CD ROMs be read by an eraseable optical disc drive? Message-ID: <6170@hub.ucsb.edu> Date: 25 Aug 90 23:44:27 GMT References: Sender: news@hub.ucsb.edu Distribution: comp Organization: University of California -- Santa Barbara Lines: 42 In-reply-to: Chuck.Phillips@FtCollins.NCR.COM's message of 23 Aug 90 08:14:14 GMT In article Chuck.Phillips@FtCollins.NCR.COM (Chuck.Phillips) writes: I just saw an ad for an erasable optical drive for the Amiga. Question: Would it be possible for the same drive to provide CD ROM functionality (compatible with the CDTV)? Is this only a matter of providing compatible functions in the whatever.device, or is there some physical incompatiblity? Sorry, not possible. The media, although similar, are different. To wit: CD-ROM's look just like the musical CD's. This is why the upcoming CDTV can also function as a standard stereo component for playing musical CD's. Read/write optical disks (I'll say "floptical," though that is very inaccurate) are the same size and shape, but they come in plastic cartridges. Take a look at one of your 3 1/2 inch floppies and imagine it in a 5 1/4 inch size with an optical disk inside, and you'll start to get the idea. The disks themselves actually look different. You can actually see the sectors laid out on a floptical, 11 per track. The recording method is entirely different. CD-ROM's are recorded by burning jillions of little pits in the plastic (I think). Flopticals are written by using a very focussed laser to heat a track to its curie point then using an ambient magnetic field to align the crystals in the substrate to the direction of the field (I think). The reading method actually somewhat similar. You see how your laser reflects off the surface of the disk. This will be different, depending on whether your crystals are aligned (new age data storage) or whether a pit has been burnt. I just want to know how the pricing is set. You can get a new NeXT for $6.5K, which includes a read-write optical drive, along with lots of ram, processors, monitors, interfaces, and whatnot. On the other hand, a Sony mechanism erasable optical drive in a SCSI box costs $4k. Why so much? -- Dan Zerkle 6600dan@ucsbuxa.ucsb.edu 6600dan@ucsbuxa.bitnet (805) 968-4683 Amiga.... Because life is too short for boring computers.