Re: 64-bit Linux On 32-bit processors

On Thu, 12 Aug 2004, wcseipelr wrote:

>    I know the Ultra 2 300 MHz and 400MHz unit run 64 bit software, Sun
> claim the 200MHz unit should not be used in the 64 bit mode. the Ultra 2
[snip]

The <= 200MHz units are UltraSparc-I cpus. They are 64bit chips and you 
can run 64bit Solaris on it if you force it to boot the 64bit kernel, 
which they will do just fine. You get more information by looking up the 
/platform/sun4u/boot.conf file on a Solaris box as to -why- the 64bit 
kernel is disabled by default on these chips:

-------------- Excerpt from /platform/sun4u/boot.conf ---------
# On systems containing 200MHz or lower UltraSPARC-I processors,
# it is possible for a user to run a 64-bit program designed to exploit a
# problem that could cause the processor to stall.  Since 64-bit programs
# cannot run on the 32-bit kernel, the 32-bit kernel is chosen as the
# default boot file 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 designed to cause a processor to stall
# may choose to run the 64-bit kernel by uncommenting the following item:
#
#ALLOW_64BIT_KERNEL_ON_UltraSPARC_1_CPU=true
-------------- Excerpt from /platform/sun4u/boot.conf ---------

Regards,

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