tjhorton@csri.toronto.edu (Tim Horton) (10/25/88)
alexis@ccnysci.UUCP (Alexis Rosen) writes: >The Optical drive is a true read-write drive... >The SCSI controller is a next-generation (no kidding...) chip which support 4.8 >MBYTES/sec. (can you say mainframe channel speeds?) Of course, I don't think >you can get a SCSI drive which transfers this fast, but that will change... Are you sure that's not 4.8M-BITS/second? From what I understand of the technology, if they are using a single laser the upper limit on reliable data transfer is 5Mbits a second, or was so just a few months ago (ref: IEEE Spectrum, early this year?). X many BITS per second would be an order of magnitude slower than BYTES; so it may not be that blindingly fast, though I do like the technology.
wb1j+@andrew.cmu.edu (William M. Bumgarner) (10/27/88)
>> Are you sure that's not 4.8M-BITS/second? From what I understand of the >> technology, if they are using a single laser the upper limit on reliable >> data transfer is 5Mbits a second, or was so just a few months ago (ref: The Floptical Drive is not on the SCSI port. It goes through its own controller. SCSI speed is independent of the Floptical port speed. b.bum wb1j+@andrew.cmu.edu
alexis@dasys1.UUCP (Alexis Rosen) (10/28/88)
In article <8810250344.AA02429@esplanade.csri.toronto.edu> tjhorton@ai.toronto.edu writes: >alexis@ccnysci.UUCP (Alexis Rosen) writes: >>The Optical drive is a true read-write drive... >>The SCSI controller is a next-generation (no kidding...) chip which support >>4.8 MBYTES/sec. (can you say mainframe channel speeds?) Of course, I don't >>think you can get a SCSI drive which transfers this fast, but that will >>change... > >Are you sure that's not 4.8M-BITS/second? From what I understand of the >technology, if they are using a single laser the upper limit on reliable >data transfer is 5Mbits a second, or was so just a few months ago (ref: >IEEE Spectrum, early this year?). Yes. I am ABSOLUTELY SURE that it is 4.8 mBytes/sec, NOT mBits. The maximum transfer rate of the Optidrive is not relevant, since (as I wrote in that same article) the Optidrive has its own DMA channel and does not go through the SCSI port. Regardless of that, the maximum rate of a SCSI port is not dependant or relevant to the speed of any individual device on it. For example, my Mac II has a SCSI port which can absorb about 300 KBytes/sec. sustained. I can get a DaynaFile SCSI Floppy unit which won't transfer more than about .5 mbit/sec. I have a Wren III which can transfer about 1 MByte/sec. sustained. Naturally, it doesn't go that fast when attached to the Mac (but it will when attached to things like Suns). ---- Alexis Rosen alexis@dasys1.UUCP or alexis@ccnysci.UUCP Writing from {allegra,philabs,cmcl2}!phri\ The Big Electric Cat uunet!dasys1!alexis Public UNIX {portal,well,sun}!hoptoad/
tjhorton@csri.toronto.edu (Tim Horton) (10/31/88)
wb1j+@andrew.cmu.edu (William M. Bumgarner) writes: >>> Are you sure that's not 4.8M-BITS/second? From what I understand of the >>> technology, if they are using a single laser the upper limit on reliable >>> data transfer is 5Mbits a second, or was so just a few months ago (ref: >The Floptical Drive is not on the SCSI port. It goes through its own >controller. SCSI speed is independent of the Floptical port speed. My comments refer to limits on the speed of the data transfer due to the medium itself, not ports or anything up or down stream. I think the upper limit on writing speed is 5 MBits/second/laser. The recording media must be heated to about 150 degrees Celsius using the right wavelengths, and that takes time.