[Info-vax] [OT] Bare metal definition, was: Re: VMS port to x86

[Simon Clubley]

On 2012-03-26, JF Mezei <jfmezei.spamnot at vaxination.ca> wrote:
> John Wallace wrote:
>
>> Oh dear, not that silliness again. Not running Windows may be better
>> than running Windows, but running a Linux layer underneath the
>> emulator doesn't make it a "bare metal" emulator.
>
> Not sure how much of linux is included in that vtAlpha "bare bones". But
> it is quite possible to really have a bare metal linux and this is
> commonly done for embedded systems, TVs, thermostats, TV decoders etc.
>

In the embedded world, bare metal has a specific meaning. When your
application is directly addressing the hardware it's running on
without any operating system between the application and the hardware,
the application is running in bare metal mode.

When your application is talking to the hardware via a operating system
supplied API, that is not bare metal mode.

One specific example: one of the boards in front of me is a Atmel SAM7S256
board (this one: http://olimex.com/dev/sam7-h256.html in case you are
interested.) When my application directly talks to the hardware registers
on this board and handles the interrupts directly, then it's running in
bare metal mode.

If I write a BSP for a RTOS and modify the same application to run on this
board under that RTOS, then the application is no longer running in bare
metal mode.

If there's a cut down Linux between your application and the hardware,
then that application is not running in bare metal mode. :-)

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world