Does ppc cpio have limit in size?

Recently I 'm using cpio filesystem (kernel and filesystem compressed
as a whole) on ppc8270 .

However I found that the bigger the size of uImage is , the easier
kernel failed when booting.

Everytime it failed when calling "populate_rootfs"  when booting, so I
guess maybe the size of uImage effect booting procedure.


Anyone know how to boot a large cpio uImage ?  Thank you!

regards,

wilbur