On UltraSPARC systems with 200MHz or lower processors, it is possible for a user to run a 64-bit program designed to exploit a problem that could cause a processor to stall. Since 64-bit programs cannot run on the Solaris 32-bit kernel, the Solaris 32-bit kernel is booted by default on these systems.
The code sequence that exploits the problem is very unusual, and is not likely to be generated by a compiler. Assembler code had to be specifically written to demonstrate the problem. It is highly unlikely that a legitimate handwritten assembler routine would use this code sequence.
Users willing to assume the risk that a user might accidentally or deliberately run a program that was designed to cause a processor to stall may choose to run the Solaris 64-bit kernel on these systems.
# /usr/sbin/psrinfo -v
You can change the default kernel from 32-bit on a system by modifying the boot policy file. Edit the /platform/platform-name/boot.conf file so that it contains an uncommented line with the variable named ALLOW_64BIT_KERNEL_ON_UltraSPARC_1_CPU set to the value true as shown in the example that follows:
See boot(1M) for more information about changing the default kernel.
You may also purchase an upgrade to your system; contact your Sun representative for details.