Chuck.Phillips@FtCollins.NCR.COM (Chuck.Phillips) (08/27/90)
First, I'd like to thank Dan Zerkle for his detailed response to my query
about using the same drive for both CD ROMs and read/write optical disks.
>>>>> On 25 Aug 90 23:44:27 GMT, 6600dan@ucsbuxa.ucsb.edu (Dan Zerkle) said:
Dan> Sorry, not possible. The media, although similar, are different. ...
Dan> Read/write optical disks (I'll say "floptical," though that is very
Dan> inaccurate) are the same size and shape, but they come in plastic
Dan> cartridges. Take a look at one of your 3 1/2 inch floppies and
Dan> imagine it in a 5 1/4 inch size with an optical disk inside, and
Dan> you'll start to get the idea.
How about a plastic case for CD ROMs to achieve physical compatibilty?
This approach has been used to allow mini VHS tapes to be played by
standard sized VHS machines (and cassettes to be played by, ugh, 8-track
machines:).
Dan> The disks themselves actually look different. You can actually see
Dan> the sectors laid out on a floptical, 11 per track.
Then, using my near negligible knowlege of SCSI, I suppose the software to
retrieve data is buried in the drive somewhere and not possible to override
on _existing_ read/write drives. (Please, someone tell me I'm wrong!)
Dan> The recording method is entirely different. ...
Attempted writes to a CD ROM should be a big no-no anyway.
Dan> The reading method actually somewhat similar. You see how your laser
Dan> reflects off the surface of the disk. This will be different,
Dan> depending on whether your crystals are aligned (new age data storage)
Dan> or whether a pit has been burnt.
Questions: Would it be possible for the same optical device to read both
types of disks? Alternately, would it be possible to physically fit the
required optics for both formats into a single box?
Would it be physically possible to design a drive fit for both formats?
(After a failed read of one format, the drive could switch to the other
automatically unpon disc insertion or simply use the disc's form factor for
deciding.) I realize now it's improbable an existing drive could work, but
I'm wondering if some enterprising hardware company out there is looking
into this. How about using a plastic adaptor and a raw Sony mechanism
(i.e. sans SCSI) with special firmware wrapped around it?
Dan> I just want to know how the pricing is set. You can get a new NeXT
Dan> for $6.5K, which includes a read-write optical drive, along with lots
Dan> of ram, processors, monitors, interfaces, and whatnot. On the other
Dan> hand, a Sony mechanism erasable optical drive in a SCSI box costs $4k.
Dan> Why so much?
At a NeXt demo, I was told Mr. Jobs got special pricing because he
committed to the technology (provided a beta site, etc.) long before it was
a viable product. However, I find it difficult to believe that either Sony
or NeXt is selling at a net loss. Hmm...so the effective price of a NeXt
_computer_ is only $2.5K, eh? Alternately, you could look at the NeXt as
an read/write optical drive with a _very_ large cache. :-)
Dan> Dan Zerkle 6600dan@ucsbuxa.ucsb.edu 6600dan@ucsbuxa.bitnet (805) 968-4683
Dan> Amiga.... Because life is too short for boring computers.
#include <usual/disclaimer.h>
--
Chuck Phillips MS440
NCR Microelectronics Chuck.Phillips%FtCollins.NCR.com
2001 Danfield Ct.
Ft. Collins, CO. 80525 uunet!ncrlnk!ncr-mpd!bach!chuckpmk59200@metso.tut.fi (Kolkka Markku Olavi) (08/27/90)
In article <CHUCK.PHILLIPS.90Aug27073200@halley.FtCollins.NCR.COM>, Chuck.Phillips@FtCollins.NCR.COM (Chuck.Phillips) writes: |> Dan> Read/write optical disks (I'll say "floptical," though that is very |> Dan> inaccurate) What an understatement! Floptical disks are MAGNETIC disks with optical tracking, they have NOTHING AT ALL in common with CD-ROMs, WORMS or rewritable optical disks. Better use the real names of things. |> Questions: Would it be possible for the same optical device to read both |> types of disks? Alternately, would it be possible to physically fit the |> required optics for both formats into a single box? This would mean fitting two separate head assemblies in the system and duplicating a lot of electronics. It wouldn't be much cheaper than using two separate drives. |> Would it be physically possible to design a drive fit for both formats? Of course it's _possible_, but if it is sensible is another question. What's wrong with using separate drives for CD-ROMs and R/W disks? -- Markku Kolkka mk59200@tut.fi
p576spz@mpirbn.mpifr-bonn.mpg.de (S.Petra Zeidler) (08/28/90)
In article <CHUCK.PHILLIPS.90Aug27073200@halley.FtCollins.NCR.COM> Chuck.Phillips@FtCollins.NCR.COM (Chuck.Phillips) writes: >Questions: Would it be possible for the same optical device to read both >types of disks? Alternately, would it be possible to physically fit the >required optics for both formats into a single box? A rewritable optical disk (magnetooptical) works this way: -writing: the laser heats a small patch of disk => the magnetic suszeptibility rises (Curie law, sp?) in that patch => a rather weak magnetic field can therefore switch the direction of the magnetic field in that patch (and in that patch only; thus you need no very fine collimated fields). After writing the patch cools and the magnetic field 'freezes' (so don't put a MOD into a hot oven >:-) -reading: a weak polarized laser, that doesn't heat the disk much, is shone onto the magnetized surface => the magnetic field twists the vector of the polarisation (Faraday effect) => the reflected light will pass an analysator (another polarisator) or not, depending which way the vector of the polarization is pointing; a photodiode measures the 'outcome' A CD is read by reflection: a laser shines onto the material and is reflected either this way or that, depending onto pit or no pit, and generates a zero or a one (and as long as you don't melt the disk down, heat or magnetic fields shouldn't harm it :) The only setup you could use both for MOD and CD reading would be the spin drive and the reading laser, but assembling both into one device could stuff the interior a bit (or make the drives larger). But why do it anyway ? It should be easier to do 5 1/4 and 3 1/2 inch floppy reading in one device and noone bothers to do that. Besides, you can use a CD ROM player for music as well; if it was also a MOD drive, it would be a bit clumsy :) (All technical details open to correction; I was only interested in the physics and didn't keep the rest) Greetings, spz --- spz@specklec.mpifr-bonn.mpg.de or spz@mpirbn.uucp or universe!local-cluster!milky-way!orionis-arm!sol!earth!uunet!unido!mpirbn!spz = S.Petra Zeidler | ... in the midst of your laughter and glee, Auf dem Huegel 69 | you will softly and suddenly vanish away, 5300 Bonn 1, FRG | and never be met with again.