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From: brim@cbmvax.commodore.com (Mike Brim - Product Assurance)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Using IDE and MFM Drives together
Message-ID: <22168@cbmvax.commodore.com>
Date: 5 Jun 91 13:17:02 GMT
References: <3200@ria.ccs.uwo.ca> <1991Jun2.045900.15627@msuinfo.cl.msu.edu> <3224@ria.ccs.uwo.ca> <1991Jun3.200840.23282@msuinfo.cl.msu.edu>
Reply-To: brim@cbmvax.commodore.com (Mike Brim - Product Assurance)
Organization: Commodore, West Chester, PA
Lines: 38

In article <1991Jun3.200840.23282@msuinfo.cl.msu.edu> draper@buster.cps.msu.edu (Patrick J Draper) writes:
> In article <3224@ria.ccs.uwo.ca> wlsmith@valve.heart.rri.uwo.ca (Wayne L. Smith) writes:
> >In article <1991Jun2.045900.15627@msuinfo.cl.msu.edu> draper@buster.cps.msu.edu (Patrick J Draper) writes:
> >>Set
> >>the BIOS type on the primary MFM drive to what it's supposed to be, and
> >>the second hard disk bios setting to NOT INSTALLED.
> >
> >I thought that IDE controllers needed the bios info.  If you set the 2'nd
> >drive bios info to -NOT INSTALLED-, how does the IDE controller/drive
> >know what's going on?  How does the computer know what's going on?
> 
> The IDE drive controller has its own BIOS on board. It doesn't need to
> know anything about the PC's BIOS.
> 
First of all discussions about IDE drives tend to be very general.  IDE drives
are simply drives that have all electronics (controller...) embedded on the 
drive.  Most of these drives do use the AT interface and most of these use
RLL 2,7 encoding.  Someone posted that IDE drives use MMFM encoding, I have 
never seen this but there may be some drives that use it.  

As far as IDE drives not using the PC's BIOS (or SETUP):  I've worked with 
over 20 diff types of IDE drives and have never seen one that does not 
require a drive type to be selected.  That doesn't mean one doesn't exists,
I just have not seen it.  If someone wants to add an IDE (AT interfaced) drive
to a system with a ST506 drive/controller, one of the controllers has to be
primary and the other secondary. Addresses and IRQ's have to be unique.  This
is no different then adding two ST506 controllers in a system.  The AT
interfaced IDE drive looks like a ST506 controller to the system.  Since it 
looks like a ST506 interface, all BIOS rules still apply.

-- 
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Disclaimer: I don't speak for my company or myself.

Mike Brim			     |	Commodore Electronics Limited
PC Analyst - System Evaluation Group | 	West Chester, PA 19380
Product Assurance		     |	InterNet: brim@cbmvax.commodore.com
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