[1436] in linux-scsi channel archive
Re: BusLogic BT-948 and UltraSCSI
daemon@ATHENA.MIT.EDU (Leonard N. Zubkoff)
Mon Feb 17 18:57:50 1997
Date: Mon, 17 Feb 1997 15:34:59 -0800
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: hpa@transmeta.com
CC: submit-linux-dev-scsi@ratatosk.yggdrasil.com
In-reply-to: <5ea80g$15v@palladium.transmeta.com> (hpa@transmeta.com)
From: hpa@transmeta.com (H. Peter Anvin)
Date: 17 Feb 1997 18:28:32 GMT
Organization: Transmeta Corporation, Santa Clara CA
I have a BusLogic BT-958 with a Seagate Ultra/Wide SCSI disk,
ST34371W. When I boot Linux, it gives me:
scsi: ***** BusLogic SCSI Driver Version 2.0.6 of 1 December 1996 *****
scsi: Copyright 1995 by Leonard N. Zubkoff <lnz@dandelion.com>
scsi0: Configuring BusLogic Model BT-958 PCI Wide Ultra SCSI Host Adapter
scsi0: Firmware Version: 5.06I, I/O Address: 0xEFF4, IRQ Channel: 11/Level
scsi0: DMA Channel: None, BIOS Address: 0xDC000, Host Adapter SCSI ID: 7
scsi0: Scatter/Gather Limit: 128 of 8192 segments, Parity Checking: Enabled
scsi0: Synchronous Initiation: Enabled, Extended Disk Translation: Enabled
scsi0: Disconnect/Reconnect: Enabled, Tagged Queuing: Enabled
scsi0: Total Queue Depth: 192, Mailboxes: 255, Initial CCBs: 64
scsi0: Tagged Queue Depth: Automatic, Untagged Queue Depth: 3
scsi0: Host Adapter SCSI Bus Termination (Low/High): Enabled/Enabled
scsi0: Error Recovery Strategy: Default
scsi0: *** BusLogic BT-958 Initialized Successfully ***
scsi0: Target 0: Synchronous at 10.0 mega-transfers/second, offset 15
scsi0: Target 6: Asynchronous
scsi0 : BusLogic BT-958
... however, AutoSCSI shows me "Negotiated rate: 20 MHz". Which is
right?
Last I checked, AutoSCSI reports in MB/second, not MHz.
a. The Linux driver displays 10 MHz but runs at 20 MHz;
b. The card knows how to do 20 MHz but the Linux driver runs
it at 10 MHz because it doesn't know higher rates;
c. The Linux driver runs the card at 10 MHz for some other
technical reason?
None of the above. The driver reports in mega-transfers/second, because it
doesn't actually know whether or not Wide negotiation has been successfully
performed. This term is taken from the SCSI specification.
Now in your particular case, AutoSCSI is reporting a 20MB/second transfer rate,
which is equal to 10.0 mega-transfers/second * 2 bytes/transfer for Wide.
However, your disk and controller should be capable of 40MB/sec or 20.0
mega-transfers/second.
With the "Factory Default" settings AutoSCSI limits devices to 10.0
mega-transfers/second (i.e. does not enable Ultra SCSI speeds). You can enable
Ultra SCSI individually for each device. Loading the "Optimal Default"
settings should also do this. I believe "Optimal Defaults" also enables SCAM,
which is generally safest left disabled.
BusLogic chose to make the "Factory Defaults" conservative since enabling
UltraSCSI speeds only works reliably when you meet the more stringent cabling
requirements, have properly implemented devices, etc. There are SCSI devices
out there which do not properly handle the synchronous negotiation for
UltraSCSI speeds.
Leonard
