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Re: Various kernel image flavours (Was: Re: debian on cobalt raq1)

Jens Seidel wrote:
> On Wed, Dec 20, 2006 at 01:30:36PM +0100, Martin Michlmayr wrote:
> > Thiemo, Peter, do you have any idea why a 2.6.18 might not work on
> > raq1?  I don't see why it would work on some Cobalt machines but not
> > on the raq1.
> Let me ask a probably very stupid question:
> Why exist so many different kernel image flavours in Debian for Mips?
> Examples:
> http://people.debian.org/~ths/d-i/mipsel/images/daily/
> http://people.debian.org/~ths/d-i/mips/images/daily/
> I know about the endian issue. But apart from it, are the
> subarchitectures really so different from each other?
> Shouldn't at least all support MIPS 1 ISA?  

The matter is most of the time not the CPU capabilities but the
different system architectures and firmware environments.

> Even if we consider also 32 vs. 64 bit kernels (or can each 64 bit hardware
> run a 32 bit kernel?)

In theory yes, but they may have registers which need 64 bit wide
accesses, or I/O space in the 64bit address range, or have more RAM
as a 32bit address space can hold. In short, it is impracticable.

> I count only 2*2 = 4 possible combinations.
> Of course it's also possible that some images are very minimalistic
> (reduced to bare minimum of driver settings) to be able to run on
> limited hardware, is this the case?

No, we usually build the full set of modules with standard settings.

> I know from Intel architectures that one common kernel together with
> a set of kernel modules is sufficent!

Only for PC-like architectures, other Intel-based systems are not
supported at all (and are out of fashion by now due to the prevalence
of the PC).


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