Path: utzoo!attcan!uunet!lll-winken!csd4.milw.wisc.edu!bionet!ames!ucsd!net1!hutch
From: hutch@net1.ucsd.edu (Jim Hutchison)
Newsgroups: comp.arch
Subject: R/W Optical questions
Message-ID: <1589@ucsd.EDU>
Date: 6 Apr 89 07:04:56 GMT
Sender: nobody@ucsd.EDU
Reply-To: hutch@net1.UUCP (Jim Hutchison)
Lines: 26
References:
Organization:

I have been reading about read/write optical disks after finding I knew
nothing about them, now I know a little.  A few things came to mind, 
and this seems to be a good place to check out the "facts".

1) In the magazine I was reading (its around here somewhere), the type
discussed was one where the media was heated with a laser in a magnetic
field and then held the field.  Writing 0's and 1's was a process of
setting the field for 0's, hitting the track (zeroing it), inverting
the field and writing the 1's.  With this in mind, does anybody switch
which step they do first to cut some of the delays in settling/stablizing
of the polarity?  Is the rotational delay long enough that this is not
even an issue (delay >> settling time)?

2) If I moved back to balmy El Cajon (which sports 100 degree weather
right now), would the constant heat be enough to allow entropy to have
an effect on the legibility of the datas state?  Similiar to the way
wood will "spontaneously" if kept warm enough long enough?

3) Is there usually some kind of interlock to make sure that the field
actually changes polarity everytime you write a sector?  Could be real
nasty if it didn't.

4) With this technology, is it possible to do an inexpensive read-after-
write?

/*    Jim Hutchison   		{dcdwest,ucbvax}!ucsd!net1!hutch  */