linux on DE2-70 with 2 blocks of sdram

hi,

DE2-70 have 2 blocks of sdram .each of them is 32mb. i want to use both of them as RAM of my system .what can i do.

As we know ,with one sdram chip,in sopc we named it DDR2_TOP.what can i do for 2.

I test it as follows :

1.allocate the address in sopc like this

sdram_1 0x0--0x1fffffff

sdram_2 0x20000000-3ffffff

2.modifiy the nios.h in linux

# define DDR2_TOP_BASE SDRAM_1_BASE

# defire DDR2_TOP_SPAN (SDRAM_1_SPAN+SDRAM_2_SPAN)

3.the kernel can generated fine

when booting ,error occur:

failure at cache_alloc_refile()

how can i fix it

thank you