Is there a Catweasel like device for hard disks?
cclist at sydex.com
Thu Jan 3 10:55:15 CST 2008
> From: Jules Richardson <jules.richardson99 at gmail.com>
> Hmm, I thought I read once that you could throw pretty much anything you
> wanted at a ST506 drive so long as it was within the various tolerances -
> is that not true of ST412-type drives?
While that may be true in theory, I'm going to guesstimate that 99
and 44/100 percent of the applications of the ST506/412 out there
used either MFM, MMFM (maybe) or 2,7 RLL for recording. While anyone
could throw together a bunch of TTL chips to record any old way on a
floppy (and did), implementing a hard disk controller with random
logic wasn't a simple matter and almost all manufacturers, by the
time of the ST506 used commodity solutions.
That's not to say that there aren't any bizarre recording schemes out
there for ST506s; just that I've never run into one.
For example, I've got a few mutually incompatible 2,7 RLL PC-AT style
controllers, but they differ more in logical details (address marks,
header layout, ECC codes) than they do in modulation methods or clock
rate. While it may have been possible to, say, employ FM recording
on a ST412, I've never seen it done in practice. There *were* some
RLL variants that attempted to push things past 2,7 (Perstor?) on a
412 interface, but they were never very reliable or popular.
Did any application of a 506 even use zoned recording (i.e. using a
faster data clock on the outer cylinders)?
More information about the cctalk