[uClinux-dev] about nommu or mmu

Fréderic DUBOIS frederic.dubois at synchronic.fr
Wed Mar 19 03:32:33 EST 2003

> -----Message d'origine-----
> De : John Williams [mailto:jwilliams at itee.uq.edu.au]
> Envoyé : mer. 19 mars 2003 06:45
> À : uclinux-dev at uclinux.org
> Objet : Re: [uClinux-dev] about nommu or mmu
> ChangDa Tong wrote:
> > I mean if more and more cpu used in the embedded device have a mmu,
> > could uclinux have less usage? Could the nommu cpu's is 
> used less in the
> > near future? Maybe this affect  the spreadness of uclinux. 
> Could anyone
> > show some facts that nommu processor is hard to be repleace 
> the nommu
> > ones?

Maybe we could add on to the credit of nommu chips, easier to program - at
least compared with what I've seen from Intel's.

> An interesting question, which could be subtitled "The future 
> of uClinux".
> To get the ball rolling, you might speculate that uClinux 
> will just go 
> deeper and deeper embedded.  At the coal face it will always be the 
> struggle of getting the necessary performance from the 
> cheapest piece of 
> hardware that will do the job.
> When the processors used in a network router (like SnapGear's 
> stuff) can 
> "afford" an MMU, then they would probably upgrade to regular linux.
> However, by that time, even smaller, cheaper and faster no-mmu 
> processors will exist, and they will be embedded in your 
> internet-ready 
> toaster.  Then, by the time the toaster manufacturer upgrades 
> to proper 
> linux, maybe you'll run uClinux in your internet enabled 
> wrist watch, or 
> the microchip embedded in your skull that reminds you to take out the 
> garbage and feed the cat.  I can see it now, tattoos reading "uClinux 
> inside"!

My cat is already featured with a built-in reminder. When he is hungry he
says: Meew!

> Of course I'm being a bit silly, but the "ubiquitous computing" folks 
> will need an OS, and uClinux might well be it.
> Remember that in the early days IBM (or so the story goes) 
> predicted the 
> global market for "computers" as being upper bounded somewhere around 
> 10.  Oh, and Bill Gates said no-one would ever need more than 
> 640K of RAM.

Well, 20 years ago people were doing things different than today - and for
these things even 64K was enough. There were no GUI, few backward
compatibility requirements, etc. and it happens to be to some extend the
same situation for embedded devices.
In our embedded world there are many kernels which fit into a bunch of
Kilobytes and do their job without mmu, and this is perfect for small, low
cost embedded devices.
Motorola and co. are marketing processors at mid range between
microcontroler and microprocessor and it seems that uClinux is one of the OS
able to fully operate them.

> Cheers,
> John

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