steele@unc.cs.unc.edu (Oliver Steele) (11/07/88)
In article <17548@shemp.CS.UCLA.EDU> casey@cs.ucla.edu (Casey Leedom) writes: > o Going with the Sony optical disk instead of the Canon because > of its higher performance and conformance to ANSI standards > (anyone have any data on the storage capacity of the Sony > disk?). 650Mb formatted, but I think that's only 325Mb per side, which isn't that much of an improvement over the Canon. That's flippy not floppy, by the way, so you only see one side on-line without manual intervention (or a jukebox). The reason for this is that each side has to spin a different way so that the synchs will be right before the sectors, &c. Some good news about the 5.25" oppies, by the way, that is probably true of the OpPIeS as well: o They don't become real fragile (magnetically) in hot weather. The intensity necessary to flip a bit at room temperature is 10K->15K oersteds, and even at 50oC it's about 5K oersteds. o They aren't real prone to dust. Dust sits on the surface of a transparent outer layer, the magnetic material is a few millimeters away. Hence, dust is out of focus. o They don't get hot. Only a few femtojoules of energy are pumped into the medium, and the heat dissipates over a few nanoseconds. o They don't wear out. People have had oppy drives continous write to a single track for 10M->30M times without failures (this is one-> three months of continuous writes). I think this beats magnetic media by a lot. o That 80msec seek time isn't necessarily as bad as it sounds. The 5.25" drives, at least, can move the focus across about 5Mb without physically moving the head, so the shorter seeks can be as low as 10msec or so. I don't know how long this happens, or if Mach is intelligent about laying out files such that it might take advantage of this. The bad news is that the 5.25" oppies cost $250 each, even though they're made by both 3M and some other company. The smaller ones will be made by Canon alone, which has never made any medium, and oppies are supposed to be harder to build than strictly-magnetic or strictly-optical media. Canon has also not agreed to Jobs's $50 price proposal. All of the above is from a lecture by Dr. Robert P. Freese, president of Alphatronics, Inc., which sells 5.25" oppies and oppy drives. Dr. Freese is knowledgable but hardly disinterested; I, on the other hand, am totally objective but know nothing of physics, optics, or hardware in general. Dr. Freese, by the way, called them "magneto-optical drives" and similarly bulky names. I prefer to call things by how they're used and not what they're made of, for which I expect some letters, which I'll ignore. --------------------------------------------------------------------------- Oliver Steele ...!decnet!mcnc!unc!steele UNC-CH steele@cs.unc.edu