[comp.misc] IDE/MFM/RLL Question

ferrick@acsu.buffalo.edu (patrick k ferrick) (12/18/90)

Could somebody please tell me what distinguishes an IDE encoding hard disk
controller from either an MFM or RLL?


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|  Patrick K. Ferrick / KA2AYK       |  Will somebody please get this         |
|  ferrick@autarchacsu.buffalo.edu   |  walking carpet out of my way ???      |
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rcd@ico.isc.com (Dick Dunn) (12/20/90)

ferrick@acsu.buffalo.edu (patrick k ferrick) writes:

> Could somebody please tell me what distinguishes an IDE encoding hard disk
> controller from either an MFM or RLL?

IDE is not an encoding technique.  IDE is a style of interface between the
PC/AT bus (the "ISA bus") and a disk drive.  It's a very simple interface--
an IDE controller is little more than an adapter to get the right signals
to/from the drive.  Most of the "controller" logic is built onto the drive
with IDE.  (It stands for "integrated drive electronics.")  The software
interface to an IDE drive looks just like the standard interface.  However,
IDE doesn't have the old-style constraint on data rate between drive and
controller that MFM and RLL do; hence IDE drives can have more than the 17
or 26 sectors/track that are conventional for MFM and RLL, resp.  This also
allows higher overall transfer rate.
-- 
Dick Dunn     rcd@ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   ...Mr. Natural says, "Use the right tool for the job."