In PPC64 there are number of problems in arch/ppc64/boot/main.c that 
prevent a kernel from making use of a large (greater than ~16MB) INITRD. 
This is 64 bit architecture and really large INITRD images should be 
possible.

Simply put the existing code has a fixed reservation (claim) address and 
once the kernel plus initrd image are large enough to pass this address 
all sorts of bad things occur. The fix is the dynamically establish the 
first claim address above the loaded kernel plus initrd (plus some 
"padding" and rounding)

mark

Signed-off-by: Mark Bellon <mbellon@mvista.com>