From owner-freebsd-current  Sat Jul 11 02:37:12 1998
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Message-ID: <19980711105643.41001@mi.uni-koeln.de>
Date: Sat, 11 Jul 1998 10:56:43 +0200
From: Stefan Esser <se@FreeBSD.ORG>
To: Chris Dillon <cdillon@wolves.k12.mo.us>,
        Julian Elischer <julian@whistle.com>
Cc: Steve Kargl <sgk@troutmask.apl.washington.edu>, current@FreeBSD.ORG,
        Stefan Esser <se@FreeBSD.ORG>
Subject: Re: TESTERS NEEDED: Softupdates looks Very good.
Mail-Followup-To: Chris Dillon <cdillon@wolves.k12.mo.us>,
	Julian Elischer <julian@whistle.com>,
	Steve Kargl <sgk@troutmask.apl.washington.edu>, current@FreeBSD.ORG,
	Stefan Esser <se@freebsd.org>
References: <Pine.BSF.3.95.980709172131.4375A-100000@current1.whistle.com> <Pine.BSF.3.96.980709202901.1676A-100000@duey.hs.wolves.k12.mo.us>
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In-Reply-To: <Pine.BSF.3.96.980709202901.1676A-100000@duey.hs.wolves.k12.mo.us>; from Chris Dillon on Thu, Jul 09, 1998 at 08:56:01PM -0500
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On 1998-07-09 20:56 -0500, Chris Dillon <cdillon@wolves.k12.mo.us> wrote:
> ncr0: <ncr 53c875 fast20 wide scsi> rev 0x03 int a irq 15 on pci0.12.0
> scbus0 at ncr0 bus 0
> scbus0 target 0 lun 0: WIDE SCSI (16 bit) enabled
> scbus0 target 0 lun 0: 10.0 MB/s (200 ns, offset 15)
> sd0 at scbus0 target 0 lun 0
> sd0: <IBM DCAS-34330W S65A> type 0 fixed SCSI 2
> sd0: Direct-Access 
> sd0: WIDE SCSI (16 bit) enabled
> sd0: 40.0 MB/s (50 ns, offset 15)
> 4134MB (8467200 512 byte sectors)

[ slightly reformatted ... ]

> I also noticed something kinda funny up there in the dmesg.  See where
> it reports scbus0 target 0 lun0 as 10.0MB/sec, then says the same
> device (sd0) is 40.0MB/sec a few lines later?  Same with sd1.

Don't worry, that's just a precaution taken by the driver code.
There have been SCSI devices that are willing to accept any 
data rate offered during negotiation, but actually can't handle
more than 5MHz. These are pre-SCSI-2 drives, which just knew 
they are *that* fast, they can handle *any* data rate offered
by the host adapter (which was at most 5MHz at that time ;-)

The driver won't negotiate data rates beyond 5MHz until the drive 
has been identified as a SCSI-2 device, and that's when another 
negotiation is started by the driver ...

Negotiations may be started by both the drive or host adapter 
at any time. But except for IBM, most vendors leave it up to 
the host system to send the first message (which the driver 
does after receiving the result of an INQUIRY command).

Regards, STefan

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