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SubjectRe: Compatible with i386/UP but optimised for i686/SMP
> Point taken.  But it's the wrong way to approach the problem by a ``one
> size fits all'' approach. It's rather the job of a Linux distribution
> makes to install the right kernel for each type of machine.
>
> Let's take a look at Redhat's kernel stuff:
> [snipped]

That's all very well if Linux is actually installed on all the machines,
individually. That's not always the case -- think of dynamic
diskless-Linux-over-NFS installations.

I'm thinking of a specific scenario that I have had to maintain in the
past:

All the company's PC run Windows normally. Occasionally there is
use for running Linux on one of these PCs, to demo a program, run a
test, run as an X terminal, diagnose hardware, or just to advocate
Linux a bit...

There is NO possibility that Linux may be installed on any of these
Windows machines. Repartitioning is out of the question, and
touching the disk at all is often not accepted. A few machines do
have Linux installed; those machines only ever run Linux.

A Linux server provides a complete diskless NFS-root installation to
any machine that requests it, on demand. Hard links and clever
scripts keep the storage requirements down, and the network
configurations for each are generated from templates. NFS swapping
is also used. These installations cannot all be prepared "by hand"
in advance because there are too many _potential_ clients, most of
which will never run Linux but we don't want to rule any out by
deciding which are supported clients and which are not.

A simple DOS program is run on any PC, off a floppy disk, which
loads the kernel over the network. The kernel autodetects the
hardware and simply boots up, not touching the client's disk.
Often, up pops Xdm and the Windows user is amazed :-) Really, it
just boots and works. Sometimes a bit of per machine configuration
is needed, but only for X and the mouse. Console mode always works.

It is not acceptable to spend time "hand installing" anything, or
going through a standard distribution installation. The
administrative time cannot be justified. (And it just works
anyway...).

Some PCs are Pentiums and PPros, some 486s, some are 386s acting as
cheap printer servers (not even a monitor or keyboard on those).

There is no central database of what machines are connected that may
wish to use this service. Often Linux is run in this way just to
find out what is in a machine! :-)

In the above scenario, I would very much like to run a kernel optimised
for the PC it is running on. That is not possible unfortunately. The
next best thing would be a kernel optimised for most of the PCs.
However it must always work with _all_ the PCs if possible. It cannot
even note the CPU type the first time a client is run, and use a kernel
optimised for that client in future, because the users (they're
programmers) have a habit of changing their computers around without
telling anyone, and fiddling with their part of the network.

That is why I am interested in an Pentium/SMP optimised kernel that is
386/UP compatible. As it was, I had to make do with the 386 compatible
kernel with FPU emulation compiled in, the lowest common denominator and
probably the largest kernel. BTW, thanks to the person who made FPU
emulation into a module recently.

-- Jamie


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