i386/52638: SCSI U320 on SMP server won't run faster than 80 MB/S without kernel panic

[Derek Ragona]

>Number:         52638
>Category:       i386
>Synopsis:       SCSI U320 on SMP server won't run faster than 80 MB/S without kernel panic
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat May 24 04:20:19 PDT 2003
>Closed-Date:
>Last-Modified:
>Originator:     Derek Ragona
>Release:        FreeBSD 5.1-BETA i386
>Organization:
>Environment:
System: FreeBSD mp2.m0nk.com 5.1-BETA FreeBSD 5.1-BETA #0: Sun May 18 15:42:40 CDT 2003 root at mp2.m0nk.com:/usr/obj/usr/src/sys/GENERICSMP i386


	Intel SE7501WV2 motherboard with SCSI onboard, it uses the Adaptec 7902 SCSI chip, This problem has been with FreeBSD 5.0 Release to Current.
>Description:
	With this motherboard, which has two Xeon hyperthreaded CPU's running at 2.66 GHz, compile a kernel from GENERIC uncommenting the two lines for SMP support.  The kernel panics when the SCSI bus is run any faster than 80 MB/s.  It drops into the debugger on boot, with 5.1 beta. In 5.0 release, it would give an error message about an invalid block and lockup.
>How-To-Repeat:
	Use a multi-processor motherboard that also has U320 SCSI, and a u320 SCSI hard drive.
	Compile and install a SMP kernel from GENERIC, uncommenting the two SMP lines.
	reboot, during the reboot set the SCSI bus in the SCSI BIOS to full speed, 320 MB/s
	Just after the SCSI devices settle you will fall into the debugger.

	If you reset the server and start to reboot, you can set the SCSI bus speed to 160 MB/s in the SCSI BIOS.
	You will have the same result as you did at 320 MB/s

	If you reset the server ans start to reboot, you can set the SCSI bus speed to 80 MB/s in the SCSI BIOS.
	The server will boot and run fine.
>Fix:

	The work around is to set the bus speed at no faster than 80 MB/s.


>Release-Note:
>Audit-Trail:
>Unformatted: