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From: rc@garbo.EBay.Sun.COM (Ran-Chi Huang)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: How does an IDE drive work ?
Message-ID: <5222@male.EBay.Sun.COM>
Date: 25 Feb 91 17:53:13 GMT
Sender: news@male.EBay.Sun.COM
Reply-To: rc@garbo.EBay.Sun.COM (Ran-Chi Huang)
Organization: Sun Microsystems, Inc.  Mt. View, Ca.
Lines: 32

Hi NetLanders,

    I'm fascinated with the so-called IDE drives. I understand that the
only thing a user has to do is to select a drive type closest to the
capacity of the actual device during the CMOS setup, and the IDE drive will
happily emulate that particular drive type. How is that done ?
Specifically, I like to know the followings:

	1. When does the drive figure out what to emulate ? At boot time ?

	2. Who does the track/head/sector remapping ? The controller
	   hardware, or the so-called expansion BIOS. Can somebody
           describe what involves in the initialization phase and normal
	   I/O operations ? Like reading the CMOS RAM, blah, blah...

	3. Does that mean IDE drives depend heavily on the DOS operating
	   environment in order to function ? If the drive fails to
	   figure out what to emulate, does it act like a generic ST506
	   disk controller ?

	4. Now, the actual disk is a total black box as far as a user is
	   concerned. What does a (high-capacity) disk look like,
	   physically ? Does it use the standard ST506 data transfer rate ?
	   Does it use a zone encoding technique, i.e. putting more sectors
	   on outer tracks, to increase overall capacity?
	   
Thanks for all the information you can provide.
--
Ran-Chi Huang			BELL:       (408) 276-5832
Sun Microsystems, M/S 3-03	DOMAIN:     rc@EBay.Sun.COM
1355 California Circle		UUCP:       ...!{sun}!rc
Milpitas, CA 95134