Subject: Re: Development for MMU-less microcontrollers.
To: Brian Rose <lists@brianrose.net>
From: Andrey Petrov <petrov@netbsd.org>
List: tech-embed
Date: 08/09/2004 15:44:55
On Mon, Aug 09, 2004 at 04:32:48PM -0400, Brian Rose wrote:
> 
> I am working with the Freescale (Motorola) Coldfire line of processors
> (52xx - without MMU's), which currently are not supported by NetBSD.
> 
> Would it be possible to make a "soft MMU" in code and enable NetBSD to run
> on a broader range of devices? I just hate to see the penguin get all the
> embedded work. Is there any technical reason why a piece of software could
> not replace a hardware MMU?
> 

No MMU means no virtual memory: no address translation, no memory
protection, no system/user mode. All you have is a single address space
and one protection level for everything. "soft MMU" won't change the
limitations.

It might be possible to place all you need inside a kernel though
and run it without user mode.

	Andrey