Path: utzoo!attcan!uunet!van-bc!sl
From: sl@van-bc.UUCP (pri=-10 Stuart Lynne)
Newsgroups: comp.unix.xenix
Subject: Re: Future Domain SCSI controller for AT bus
Keywords: A friend of mine and I are looking for a '386 replacement
Message-ID: <1913@van-bc.UUCP>
Date: 11 Oct 88 22:35:41 GMT
References: <522@m3.mfci.UUCP> <1996@spdcc.COM> <213@ispi.UUCP>
Reply-To: sl@van-bc.UUCP (pri=-10 Stuart Lynne)
Organization: Wimsey Associates, Vancouver, BC.
Lines: 30

In article <213@ispi.UUCP> jbayer@ispi.UUCP (id for use with uunet/usenet) writes:
>In article <1996@spdcc.COM>, dyer@spdcc.COM (Steve Dyer) writes:
 
>> it works is a little weird.  Apparently the current (< 2.3) versions
>> of XENIX are said to "only support two drives (of any type)".  This
>> would mean that if you have a AT floppy/hard disk controller with
>> at least one of the disks in use, you don't have the option of adding
>> another controller of any type.  Now, no one can really tell me why

>The problem is not Xenix, but the way IBM designed the AT.  What happens
>is that most controllers use the same interrupt.  The AT cannot support
>multiple devices with the same interrupt.  Also, they both might be using

Well, yes and no, there are various techniques that can be used both at the
hardware and software levels to allow multiple devices to use the same
interrupt. 

Most likely the driver just can't support two controllers. You *can*
configure hard disk controllers to an alternate io location, so supporting
two boards is at least *theoretically* possible. 

In point of fact the System V / 386 system actually asks what controller you
are adding a disk to, and in the header files there is a bunch of stuff
which indicate that the driver might support two boards. Never got a chance
to try it though. And that may have been there to support something on the
Intel MultiBus 386 machine.


-- 
Stuart.Lynne@wimsey.bc.ca {ubc-cs,uunet}!van-bc!sl     Vancouver,BC,604-937-7532