Linux on PPC

Wolfgang Denk wd at
Sat Mar 4 13:05:29 EST 2006

In message <44087473.6020905 at> you wrote:
> > Many memory maps (especially those provides with some eval boards for
> > demonstration purpose) will NOT work with Linux.  Remember  that  the
> > memory  map  is  usually  not  cast  in  silicon,  but implemented in
> > software, so you can change it as needed.
> Right, thats I made sure to say; Physical Memory Map.

That's what I mean: the physical memory map  is  usually  set  up  in
software, so it can be changed to your needs.

> For example, on the Artesyn manual on their PrPMC they give a
> physical memory map, and in the Yosemite board, there is a
> physical memory map. I know many of the memory areas can be
> redefined in hardware to have a different memory location, but
> its still a physical address.

...which usually can be reprogrammed in software.

> Now, when the bootloader loads, eg. U-Boot, it sets up the
> memory management. Now this is where my understanding gets
> shakey, since I haven't looked at much of the code, so perhaps
> you can clarify. The translation unit (TLB) maps virtual addresses
> (or should that be MMU output addresses) into physical addresses,

U-Boot usually does not use the MMU. 

> What are the basic requirements for a Linux memory map then?

See the FAQ.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at
It is surely a great calamity for  a  human  being  to  have  no  ob-
sessions.                                                - Robert Bly

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