Date: Mon, 07 Jun 1999 09:55:50 -0400 From: dledford@redhat.com To: "Robert W. Rowe" <rrowe@winstar.com> Cc: Jonathan Stimmel <jstimmel@taos.com>, "J. Alan Eldridge" <alane@wozzle.geeksrus.net>, aic7xxx@FreeBSD.ORG Subject: Re: aha2930u2 Message-ID: <375BCF66.59D5AE16@redhat.com> References: <Pine.A41.3.96.990606095531.48952A-100000@vcmr-19.rcs.rpi.edu> <3.0.5.32.19990607084216.009ca780@mail.winstar.com>
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"Robert W. Rowe" wrote:
>
> Thank you very much for a comprehensive reply.
>
> My problem is an on-the-motherboard aic7895 controller. I have two SCSI3
> disks on the wide channel A and two narrow devices, a CD-RW and a Zip
> drive, on the 50-pin side.
>
> As many people who have aic789x cards have complained, I have timing
> problems. The SCSI bus continually resets, etc. I was unable to install
> RH 6.0 without disconnecting the narrow devices. With the narrow devices
> attached, the installation sequence went off into limbo during the
> disk-formatting phase.
>
> The SCSI card (on the motherboard) boots up in this order, with everything
> connected:
>
> Wide SCSI Disk 0
> CD-RW Disk 2
> Zip Disk 5
> Wide SCSI Disk 6
>
> which Linux recognizes as /dev/sda, /dev/scd0, /dev/sdb and /dev/sdc.
>
> However, when I removed the narrow devices so I could load RH 6.0, the
> second wide SCSI, still ID'd as Disk 6, became /dev/sdb in Linux. When
> everything was loaded and I wanted to see if the timing problems still were
> a factor, I plugged the narrow devices back in and turned on the machine.
> The Zip drive came up as /dev/sdb and the second wide SCSI as /dev/sdc.
> Naturally, Linux couldn't boot.
>
> I have three options:
>
> 1. Figure out how to get the zip drive to come up third in the SCSI disk
> sequence and be /dev/sdc. However, I will most likely still have timing
> problems.
>
> 2. I have an Adaptec ISA 1520 card. If it will work, if I can figure out
> how to get Linux to recognize it, put that in the machine and attach the
> narrow devices to it.
>
> 3. Turn off the Adaptec 7895 and put in a Buslogic (or whatever they are
> called now) card.
>
> The 7895 has been a problem from the time I got the computer. I have two
> EIDE drives, one now used for Win95 and the other used for daily backup. I
> also have an ATAPI CD reader because I couldn't get the SCSI CD-RW to work
> with the 7895. When I had RH 5.2, I ran Linux off the smaller EIDE drive
> and set up raid0 on two narrow SCSI fireballs. Now I have RH 6.0 set up on
> two IBM wide SCSI's, no raid.
>
> I want to get narrow SCSI working because I want to be able to burn a CD
> now and then, and because I want to put a SCSI scanner on the system.
>
> Thanks.
OK...here's the deal. The 7895 is a dual channel controller. Most
motherboards put two wide connectors on the motherboard (one for each channel)
and only one narrow connector on the motherboard (that shares the bus with one
of the wide connectors). You are evidently using the wide connector that goes
with the same channel as the narrow connector because when you plug the narrow
cable in you see your devices detected in different sequence. The also means
that your termination requirements are changing when you plug in that narrow
connector. My guess about the unreliability is that termination is not
getting set properly when you have the narrow cable plugged in. Most aic7895
motherboard implementations I've seen require you to manually set the
termination in the Adaptec BIOS because they don't support the Auto
Termination option. That means that whenever you plug in that narrow cable,
you need to go into your Adaptec BIOS and set termination to either Disabled
or High On/Low Off depending on what the BIOS gives you choices of (some
BIOSes will only give you the choice of Enabled/Disabled others give the more
techinically accurate but no more helpful version of Low On/High On,Low
Off/High On). That should solve the problem with installing with the narrow
cable plugged in (however, please note that you should check your computer's
BIOS for setting options as well, I know on the DK440LX motherboard with a
built in 7895 controller you need to disable the termination in the Adaptec
BIOS *and* you need to disable it in the computer's BIOS, in the screen where
the computer's BIOS lets you set if the aic7895 is enabled or not, they have a
second option for the termination on that channel that needs set).
But, that doesn't do you the most good. If at all possible, I would try to
use the second wide connector on the motherboard (I'm assuming there is one)
to plug the wide drives into so that the narrow drives and the wide drives
aren't sharing a channel. Then, since that likely will mean the hard drives
will be on Channel B and the narrow stuff on Channel A, go into the Adaptec
BIOS and set it to boot from Channel B first and that should cause the linux
driver to put them in the correct order for you (assuming that the linux
driver can read a SEEPROM on this controller).
That should get your particular problems taken care of.
--
Doug Ledford <dledford@redhat.com>
Opinions expressed are my own, but
they should be everybody's.
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