With System Controller firmware 5.11.4 and below, if SSC0 fails and you attempt 
to use SSC1 as the primary system controller, you will encounter random system 
board, repeater board, and/or I/O boat failures when running POST.  These 
failures will not be consistent and can change depending on the platform 
configuration.  It is believed at this time, that rebooting a domain when SSC1
is the primary controller will cause the reboot to fail because POST will fail during 
the reboot.            

At this time, System Controller 1 is only useful for automatic clock failover. 
If System Controller 0 fails you should schedule downtime for the domains to
replace System Controller 0.   Also note that at this time it is not possible
to hot swap SSC0 if SSC1 is present.  This should be fixed in future revisions
of the System Controller firmware.            

This entry is from http://cccweb.ebay.sun.com/ccc/groups/sunfire/srdbs/

Date: 2001-05-10

Written by: Frank Cerrito, frank.cerrito@Central & Joe Carr, joe.carr@Central

Submitted by: Bob Hilliard, bob.hilliard@East