[comp.sys.mac.hardware] change HD inteleave in software

minich@d.cs.okstate.edu (Robert Minich) (10/05/90)

umcarls9@ccu.umanitoba.ca (Charles Carlson) writes:
|Does anyone know if Norton Utilities allows you to look at/change the
|interleave without reformatting?

emmayche@dhw68k.cts.com (Mark Hartman) writes:
|Generally speaking, this is not possible to do.  Interleaving describes
|the number of sectors which are read out of the number that pass beneath
|the r/w heads.  So, for example, an interleave of 1:3 takes three turns
|of the disk to read the entire track.  Needless to say, the sectors are
|positioned in a like manner; i.e., sector "1" and sector "2" have two
|other physical sectors between them.
|
|While I suppose you *could* change the interleave factor, the amount of
|data shuffling you'd have to do to make it work properly really wouldn't
|be worth the hassle.
 
by umcarls9@ccu.umanitoba.ca (Charles Carlson):
| Of course its possible to do!  There are countless programs available for the
| PC to do it!  
| What data shuffling are you talking about?  All you simply have to do is:
| 1) read the track into memory
| 2) reformat track to desired interleave
| 3) write data back to disk.
|  
| Which would be quicker and easier?  That or:
| 1) backing up drive <which you should do anyways before something like this>
| 2) reformat old drive
| 3) restore all the data.

  One may be able to redo a PC hard drive's interleave "on the fly" but SCSI in
general knows nothing of tracks/sectors/cylinders/etc. It knows about blocks.
Even if the Mac's OS could, say, figure out to use every other block, it would
still be a big lose since it could no longer give out SCSI commands like "read
blocks 20-73" which lets the drive itself figure out where the blocks are. The
**EASIEST** way to do this is take your HD (or Mac, if it's an internal) to your
friendly local dealer who proabably has a bunch of free disk space somewhere
(ask about Syquest catridges!) and copy everything from your drive to his. Then
reformat your disk and copy it back. Don't forget to buy something from the
dealer, like a mouse pad, so he doesn't feel completely used. :-)  You could
probably accomplish the same thing wherever you have access to lots of disk
space (AppleShare?) but this method only takes an hour or so total.
  The Real (tm) solution to the whole interleave problem, IMHO, is to get a hard
disk with a cache built in, like a Quantum. That way it can feed a slower Mac as
fast as the Mac can swallow instead of at some function of the rotation speed.
And you can move from machine to machine and be assured you'll have the best
performance you can get from the drive.
-- 
|_    /| | Robert Minich            |
|\'o.O'  | Oklahoma State University| A fanatic is one who sticks to 
|=(___)= | minich@d.cs.okstate.edu  | his guns -- whether they are 
|   U    | - Ackphtth               | loaded or not.