Subject: Re: coldfire port of NetBSD?
To: Rob Healey <email@example.com>
From: Matthew Orgass <firstname.lastname@example.org>
Date: 09/13/2000 00:43:35
On Tue, 12 Sep 2000, Rob Healey wrote:
> Are any of the mips ports on handhelds/game controllers running
> without an MMU?
No. CPUs without MMUs tend to be quite slow anyway, and even game
controllers come with a MMU now.
> I assume you'd need to generate totally relatively addressed
> object code and do some pretty fancy bus/memory signal footwork without
> an MMU.
I don't know the modern theories on this, but my first thought would be
for the kernel to examine the binary and change any instruction that could
access a restricted or mmaped area or the code segment to first jump to
code that checks if it does and deals appropriately. I suspect you could
do better then 10% runtime overhead on most programs plus substantial
overhead the first time a binary is run.
However, even if you did all the work to make things work like usual,
it wouldn't really be NetBSD since there would be a whole lot of MI code
that you couldn't or wouldn't want to use.