*BSD News Article 83635


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From: jca@bighorn.accessnv.com (J.C. Archambeau)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: FreeBSD 2.1.5/EISA/AHA1740 not finding drives
Date: 26 Nov 1996 19:31:08 GMT
Organization: Access Nevada Inc.
Lines: 45
Message-ID: <57fght$le8@raven.eva.net>
References: <329B228D.167EB0E7@microware.com>
NNTP-Posting-Host: bighorn.accessnv.com
X-Newsreader: TIN [version 1.2 PL2]

Kim Kempf (kim@microware.com) wrote:

: I'm trying to install FreeBSD 2.1.5 on an EISA system with a AHA1740
: scsi controller.  The system is running DOS/Win95 with no problems from
: two scsi drives (540mg Maxtor, 1.0GB seagate).  I've made a boot floppy
: to boot the install.  It finds the device ahb0, but it can't find any
: drives.  Maybe the controller needs to be configured a certain way in
: the EISA setup?  Anyone have one of these running?

Do you have the board configured in enhanced EISA mode or 1542B mode?
There's a single jumper on it to switch between 1542B and enhanced
EISA mode.  Try running it as a 1542B without pulling the board out
and see what happens.  If it works, then you have it in 1542B mode.

Also, check ECU and see what it says is in the slot.  Remember, EISA
is a PnP bus similiar to MCA and PCI.  Perhaps you have it configured
for a port address, IRQ, DMA and BIOS other than the defaults which is
causing the conflict.  The 174x family has the same defaults as the
AHA-154x family; port 330h, IRQ 11 (edge triggered), DMA 5 and BIOS
DC000.

Make sure that you're using edge triggered and not level triggered
interrupts with the board.  Adaptec has a section on their webpage that
not all EISA systems support the full EISA bus spec, the biggest offender
being that many EISA motherboards do not support level triggered IRQs 
correctly or at all.  You might be able to fake it under MS-DOS/Win95.
But a lot of faking you do from MS-DOS you can't do under any flavor of
Unix.

The IRQ mode you also check from ECU.  Adaptec also has an updated EISA
config file for the 174x on their website to force the 174x to go into edge
triggered IRQ mode which eliminates the problem completely.  You only
really need level triggered IRQs in EISA if you're doing IRQ sharing and
even then the device driver has to support it plus your motherboard has
to impliment it correctly in hardware.

To my knowledge, FreeBSD doesn't support EISA level triggered IRQs.  The
only benefit you'll get from EISA is burst DMA at 33 Mb/sec and you won't
need bounce buffers for DMA transfers into the physical address space above
16 Mb.
--
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