Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!think.com!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!ames!ucsd!dog.ee.lbl.gov!nosc!crash!pnet01!jca
From: jca@pnet01.cts.com (John C. Archambeau)
Newsgroups: comp.os.minix
Subject: Re: IDE disks
Message-ID: <7632@crash.cts.com>
Date: 18 Feb 91 20:56:09 GMT
Sender: root@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 56

kjh@pollux.usc.edu (Kenneth J. Hendrickson) writes:
>In article <1627@pdxgate.UUCP> martine@jove.cs.pdx.edu (Martine Wedlake) writes:
>>	When I boot any of the boot disks I get "Read  Error.   Automatic
>>	Reboot"  and  the system tries to reboot (which of course fails).
>>	The boot disks do work on  other  machines  such  as  a  386  and
>>	turbo-88 board.  I am running an AT clone with an IDE hard/floppy
>>	controller.
>
>I asked this question before, but never got any definitive answers.
>
>Just exactly what is an IDE drive/controller?
>Does it look like MFM?  RLL?  SCSI?  ESDI?  Something else?
>Does it need a new device driver?
>Will any of the existing device drivers work?

IDE is an adaptor.  In technical terms it's a hybrid of ST412/506 (some say
ESDI) and SCSI.  It basically makes your drive an extension of the ISA bus.
The implementation is neat since in IDE translation mode it looks like a
standard ST412/506 MFM drive to your BIOS.

For example, a Conner CP-3184 has a translation mode that maps itself to the
drive geometry of a Seagate ST4096.  Very standard drive type.

As for drivers, that all depends on how intimate your ST412/506 driver is with
the controller.  I imagine that at_wini.c is pretty intimate.  Novell ELS
Level I doesn't support IDE, but it works with ST412/506 with no problems.

Again your mileage varies.  Considering the 'hardcoded' nature of the Minix
hard drive drivers, I don't think you can safely interchange ST412/506 MFM and
IDE.  This is based on my observations on the net and back about a year or so
ago when I was still playing with Minix.

If you really want to test out how compatable at_wini.c is.  Try this little
experiment.  Pull a WD1003-IWH from a Compaq and remove your WD1003-WA2 (or
MM2) and put in an IDE adaptor with a floppy drive port on it.  Effectively,
this should be identical to a WD1003-WA2 (or MM2) and an ST412/506 MFM
controller.

The WD1003-IWH is an ST412/506 to IDE adaptor board.  I've found them in
Compaq Portable II's with the 20 Mb Miniscribe 8425.  I've tested these things
with ISC 2.0.2 and it works just as well (if not a little better, haven't
benched out the throughput) as the same ST412/506 MFM drive with a
WD1003-WA2.

Again, your mileage may (and often will) vary.

     // JCA

 /*
 **--------------------------------------------------------------------------*
 ** Flames  : /dev/null                     | What to buy?
 ** ARPANET : crash!pnet01!jca@nosc.mil     | EISA or MCA?
 ** INTERNET: jca@pnet01.cts.com            | When will the bus wars end?
 ** UUCP    : {nosc ucsd hplabs!hp-sdd}!crash!pnet01!jca
 **--------------------------------------------------------------------------*
 */