[rescue] Ultra1 OBP firmware message on installation boot

[Curtis H. Wilbar Jr.]

Keep in mind there is an issue on Ultra-1 machines in 64 bit mode
where a userland assembly language program can do something bad
to the machine (I think it can halt the cpu).  This problem is
not present when running in 32 bit mode.

This is documented out there on the web somewhere.  If users will not
be allowed logins to the box (i.e. a web server only allowing http and
maybe ftp) then that won't be a problem.

-- Curt

>Date: Thu, 13 Feb 2003 19:48:01 +1100
>From: Sid Odgers <sunrescue at dysphoria.eu.org>
>To: patrick at zill.net, The Rescue List <rescue at sunhelp.org>
>Subject: Re: [rescue] Ultra1 OBP firmware message on installation boot
>User-Agent: Mutt/1.4i
>
>Yea,
>
>In terms of performance, unless you're doing heavily memory bound
>jobs (ie processes which require more than 4GB of VM) or compute
>jobs which use 64 bit integers or floats, you'd be hard pressed
>to notice the difference.  If you ARE, then 64 bit computation
>will be orders of magnitude faster (1 64-bit instruction takes
>the place of 3 or 4 32-bit instructions which emulate the
>64-bit instructions for long double(?) and long long types),
>and large datasets will be unusable as a 64-bit memory pointer
>is required to use more than 4GB of VM on flat architectures (
>and it's usually not worth the performance hit on segmented
>architectures like the newer IA32 stuff which, from memory,
>has a 4 bit segment offset pointer in the LDT, allowing you
>to address more than 4GB of VM in 4GB chunks)
>
>Nonetheless, 64-bit mode is 'cooler', and the (minimal) performance
>hit you take for running 64 bit code instead of 32 bit code isn't
>going to be noticable either way on a 1/170. :)
>
>On Thu, Feb 13, 2003 at 02:25:53AM -0500, Patrick Giagnocavo +1.717.201.3366 
wrote:
>> I am loading Solaris 9 on an Ultra1/170 with OBP 3.5 .
>> 
>> On boot, the installer gives a message about using the 32bit OS
>> instead of 64bit OS.
>> 
>> I googled and found out how to change it, but my question is, is there
>> a performance difference between the 2 kernels?  
>> 
>> I will be doing some PostgreSQL and web serving and some Perl (spit).
>> 
>> --Patrick
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