[U-Boot-Users] MMU setup in u-boot

Chris Hallinan clh at net1plus.com
Mon May 12 16:20:56 CEST 2003

John Ashfield wrote:
> u-boot setups MMU for maximum of 256M memory using Block Address
> Translation. Do you have any idea how to setup MMU for
> more than 256M (for
> example 1G of memory)?

You did not specify which processor, but in any case, the answer can
be found in your processor manaul.  For example, for the 603e core,
found in many Motorola embedded PowerPC processors, you cannot
access more than 256 MB using a single BAT register.  I believe this
is a PowerPC architectural limitation.  However, you might be able
to juggle your system resources/configuration to use more than one
BAT for mapping in memory.  There are four pairs of BAT registers
used for translating data accesses, and another four pairs for
instruction accesses.  See "PowerPC Microprocessor Family: The
Programming Environments" (the green book) and your processor manual
for details.


Chris Hallinan
DS4.COM, Inc.

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