building very small

Richard Richard at reika.demon.co.uk
Thu Jun 29 11:46:55 PDT 2000


> Our company currently has an embedded product built around a very small
> kernel from US Software.  This product runs on a 386EX processor with only
> 1MB of RAM and 1MB of paged FLASH.  I am investigating the possibilities
of
> building this same system to run on Linux.  The needs are small (no vga,
no
> keyboard, no mouse, limited interfaces (coms and networking)), but are
> interested in building with a 32bit environment (this precludes LEM) so we
> can scale up easily to some of our larger platforms including Pentium
based
> systems.  Has anybody worked closely with really!!! shrinking the Linux
core
> to its minimum?  Does anyone have a feel for whether or not this may be
> do-able?  I figure the core, with networking and coms drivers (and
> preferably the loader) must fit under 500K!
>
> Regards, MAD

I tried to check my facts before posting, but I find reading Intel
documentation painful
at the best of times, and looking for the bits they missed out is even
worse. So from
memory, the i386EX has no MMU. (I read the spec's once, about five years ago
so
I may be wrong)

The following is quoted from the release note for linux kernel
2.4.0-something:

] Surprisingly, I do get a number of questions about pre-386 Linux. The
answer,
]  at least right now, is that there is no such animal. A sister project,
ELKS
] (Embedable Linux Kernel Subset) is working to make a Linux-like operating
] system run on these machines, including protected mode support for chips
that
] support it. This project is separate from Linux-proper however and is
outside
] the scope of this document.
]
] A separate port of the Linux kernel, called uLinux, also exists and is
working to
] provide Linux on embedded and older processors, including processors
without
] MMUs. The work presently is based around the Linux 2.0 kernel and has
largely
] not been integrated into the master tree.


Hope that does not spoil your day too much

Richard


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