[LinuxBIOS] Overview

[Peter Stuge]

On Tue, Apr 25, 2006 at 01:11:55PM +0100, m at de-minimis.co.uk wrote:
> 
> Dear All,
> 
> I'm completely new to LinuxBios, and I'm trying to understand
> exactly what it does, and what it offers.  Trying to decide exactly
> how interested I am.  Could you please forgive my ignorance and
> clarify the following for me please:

Perhaps you've already checked out the wiki on
http://wiki.linuxbios.org/ ? It has useful information both on macro
and micro levels.


> Does LinuxBios run on the main processor or on some auxiliary processor?

On the main processor.


> What is the typical power consumption of a LinuxBios moboard
> running the minimum number of devices to do basic communication
> over ethernet - hopefully only the moboard and the network card if
> it isn't already on the moboard will require power, then I need to
> know processor consumption - here the earlier question about what
> does the processing becomes relevant.

This depends completely on the hardware. LinuxBIOS can be configured
to disable or just disregard any hardware in the system that can be
disabled (usually this means leaving PCI devices untouched) but
whether the hardware does powersaving or not is outside LinuxBIOS'
control.


> Can LinuxBios be used to do complicated wake-on lan?  Here minimal
> power consumption in the idle state becomes important to me. 
> (question of fairly high interest to me)

LinuxBIOS doesn't generally stay resident in any way after starting
the OS either, the exception may be the recent VSA support that is
specific to the Geode family of System-on-Chip products from AMD.

Since LinuxBIOS is no longer running, this depends on the OS.


> Does LinuxBios help with running multiple operating systems
> simultaneously? (high interest)

No.


> Does it accelerate booting, because where previously first the bios
> loaded, then grub, then the OS proper, now perhaps booting can go
> straight from LinuxBios to OS?

Yes. I believe the boot time record is around three (3) seconds
although this will require ideal circumstances. Expect LinuxBIOS to
always be faster than a factory-supplied closed-source BIOS though.
Boot time varies heavily with specific mainboards and their quirks,
which affect LinuxBIOS as well as the OS. Solid-state storage (flash)
is a must for the optimal times.


> How often can one typically write to the bios before it won't take
> any more changes?  I understand it's flash, so I expect few
> thousand times, more if one rotates which memory blocks one uses,
> but on the other hand this isn't exactly flash that is designed to
> be rewritten very often, as far as I understand anyway!

I'd expect at the very least tens of thousands write cycles, but more
commonly hundreds of thousands. Anyway it's more than enough for
development, but probably not something you would want to depend on
in the field. (self-flashing systems etc.)


> Can one fairly easily and at a competitive price buy replacement
> chips?

Lots of flash parts are interchangeable. Check the specs for the
factory-installed part and find a replacement from your favorite
flash manufacturer. Add support to the LinuxBIOS auxiliary utility
flashrom if the particular chip isn't supported yet.

Most if not all flash manufacturers have distributors that will
gladly sell large quantities (1k+) of chips. Those willing to deal in
smaller quantities are fewer, but still exist. You'll usually have to
buy at least one full package. (typically PLCC or DIP plastic tubes
with 20-40 chips) Prices depend on flash size, but stay around a few
dollars per part.


> A short introduction is probably in order:  I'm a mathematician, so
> a bit of an amateur where computer science is concerned.  I'm
> getting into writing linux device drivers at the moment.

Cool. Out of curiosity, what is your interest in LinuxBIOS?


//Peter