JWANKERL@UTCVM.BITNET (Josef Wankerl) (01/13/89)
I just finished seeing a demo of the NeXT computer work station.
The thing that really caught my eye was the Optical Drive system.
Now I know the basic theory behind reading from a CD, but how do you
go about re-writing information back?
The NeXT machine mainly used a Winchester hard drive for it's disk
I/O because it was a little bit faster, but that was only because of the
operating system version (0.6, but they now have 0.8 out).
Can anyone explain to me how the drive writes back?
-Gonzoshawn@pnet51.cts.com (Shawn Stanley) (01/18/89)
JWANKERL@UTCVM.BITNET (Josef Wankerl) writes: > I just finished seeing a demo of the NeXT computer work station. >The thing that really caught my eye was the Optical Drive system. >Now I know the basic theory behind reading from a CD, but how do you >go about re-writing information back? Byte, November 1988/Tom Thompson and Nick Baran The optical platter is composed of the same clear rigit polycarbonate material that's used in CD-ROMs. Embedded within the platter is a layer of reflective aluminum backing that's overlaid with a magneto-optical substrate.... How does the magneto-optical drive work? A single laser performs both read and write operations. To write data to the disk, the drive first applies a magnetic field to the platter. The orientation of the magnetic field determines the data to be written to the platter--either a 0 or a 1. The magnetic field is first oriented to write 0s at the start of what's called the erase pass. The laser uses a high-power beam to heat a sector on the platter's substrate to its Curie point--the temperature at which the crystals in the substrate "forget" their previous orientation and reorient themselves to the surrounding magnetic field. All the data in the target sector is thus erased to 0s. Next, the magnetic field is oriented to write 1s in the write pass, and at every spot in the sector where a bit must be set to a 1, the laser again heats the substrate to the Curie point. Finally, the sector is read in a verify pass to check toe accuracy of the data. > The NeXT machine mainly used a Winchester hard drive for it's disk >I/O because it was a little bit faster, but that was only because of the >operating system version (0.6, but they now have 0.8 out). I hear the average track-to-track seek time with the optical drive is over 65 ms. That's pretty slow, for a large-capacity media. Can anyone confirm/deny this? UUCP: {rosevax, crash}!orbit!pnet51!shawn INET: shawn@pnet51.cts.com
kamath@reed.UUCP (Sean Kamath) (01/24/89)
In article <8901132000.aa00971@SMOKE.BRL.MIL> JWANKERL@UTCVM.BITNET (Josef Wankerl) writes: > > I just finished seeing a demo of the NeXT computer work station. >The thing that really caught my eye was the Optical Drive system. >Now I know the basic theory behind reading from a CD, but how do you >go about re-writing information back? You mean it caught your ear -- it sounds like a radiator! :-) > The NeXT machine mainly used a Winchester hard drive for it's disk >I/O because it was a little bit faster, but that was only because of the >operating system version (0.6, but they now have 0.8 out). You can have just optical disk NeXT boxes, liek the one next to me, but *jjjjeeeeeezzzzzz* is it S-L-O-W!!! if 0.8 is faster, man am I glad I never saw 0.6! > -Gonzo Sean Kamath -- UUCP: {decvax allegra ucbcad ucbvax hplabs}!tektronix!reed!kamath CSNET: reed!kamath@Tektronix.CSNET || BITNET: kamath@reed.BITNET ARPA: kamath%reed.bitnet@cunyvm.cuny.edu US Snail: 3934 SE Boise, Portland, OR 97202-3126 (I hate 4 line .sigs!)