[gentoo-amd64] Re: OS setting in BIOS

[Duncan]

Peter Humphrey <peter@××××××××××××××.org> posted
200805251240.17699.peter@××××××××××××××.org, excerpted below, on  Sun, 25
May 2008 12:40:17 +0100:

> I was poking around in my BIOS this morning and rediscovered a setting
> to define the installed OS. I'd wondered about it some time ago and then
> forgotten about it.
>
> I can set the BIOS setting "OS Installation" to "Other" or to "64bit
> Linux 2.6.9". I have it set to Other at the moment. My questions are:
> what effect this setting is likely to have, and whether it's really
> specific to the version.
>
> This is a Supermicro H8DCE motherboard with dual Opteron 246s and 4GB
> RAM in four banks, two connected to each CPU.
>
> I've tried Google but found nothing.

Hmm...  The most apropos thing I could find with Linux 2.6.9 was that it 
introduced AMD dual-core support.  This of course assumes that your board 
is upgradable to dual-cores or that's obviously /not/ what it's 
referencing.   Anyway, Opteron 246s are still single-cores, so if that's 
it, the setting probably won't matter to you at this point.  However, if 
you upgrade to dual-cores, you may wish to try toggling that setting 
along with your kernel config updates turning on multi-core support, or 
it's likely not to work quite as efficiently.  

I'm guessing the alternative presents the cores as separate CPUs, less 
confusing for the OS if it didn't know about multi-cores, but not as 
efficient scheduling as you'd get with the kernel's multi-core scheduling 
support, which with multi-core scheduling enabled, knows they are on the 
same chip and thus that it costs less to transfer a job from one core to 
the other than to a core on another chip.

I'm not sure about it, but the more I think about it, the more likely 
that possibility seems to me.  If that's not it, it's sure a good fit for 
the bit we /do/ know, that (1) the option is 64-bit related (the option 
says so), that (2) it's a kernel 2.6.9 change (the option says so), that 
(3) it's Linux specific (the option says so), that (4) it's an AMD 
system, and that (5) the matching kernel (2+3) added support for the 
matching brand (4) and that it was 64-bit related (1).  If that's a 
simply coincidental set of matches, it's VERY coincidental.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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