Alicia da Conceicao wrote:
>>> Linux, or more specifically uClinux and other variations,
>>> support embedded systems with no MMU (Memory Management
>>> Units).  How hard would it be to port NetBSD to them non-MMU's
>>> systems?  What steps, work would be needed?  Has anyone else
>>> attempted this, or is working on this now?
Perry E. Metzger wrote:
>> We (Wasabi Systems) have thought about it a few times, but it is
>> becoming so cheap to have an MMU in a system that we're not sure it is
>> worth the effort. Were enough people interested (especially, I hate to
>> put it this way, paying customers -- we do have to eat) we might be
>> willing to give it a go. However, we haven't had much serious interest
>> and (as I've said) as hardware costs for MMUs fall it becomes less and
>> less interesting as projects go.
> Wes Peters write:
> Plus, even embedded developers are beginning to realize that features
> like process memory protection are a good idea.  When the incremental
> hardware cost is so small and the resulting software engineering 
> benefit so large, it becomes pretty easy to justify using a processor
> with an MMU.

Well, adding an MMU will add about an extra (US)$20 to the cost of
an embedded system.  Considering that Future Shop Canada was
selling SMC Barricades with 1 port WAN + 4 port LAN DSL/Cable-Modem
routers for (CA)$69, less then (US)$50 during their boxing week
sale, the extra $20 cost for an MMU makes a critical difference in
the embedded space.  Currently uClinux is the only opensource
Unix-OS for the embedded space.  All of the other embedded OS's
like Windriver and Windows Embedded XP are commercial.  Keep in
mind we are talking about systems where the entire kernel and
userland fits in less than 2MB of flash memory, and have only
2-4 MB of RAM to run everything.

Anyways my question wasn't whether or not it was commerically
viable for Wasabi Systems to develop a NetBSD MMU-less port.
The folks at Wasabi are incredible brilliant, and I have great
respect for them, but it may be more benifical to have people
experienced with very small embedded systems to work on a NetBSD
port, since it might be commerically beneficial for them to do
so, as oppose to paying licencing fees to Windriver.

What I would really like to know is what steps are neccessary
to put together a NetBSD port for small non-MMU systems, like
Samsung-ARM.  And I would like to know if there is any existing
work that someone might have done in on this in the past, that
might help.  Thing of these as a feasibility study to estimate
how much work in involved and what is need for a NetBSD non-MMU
port.

Thanks in advance.

Alicia.