We have have a custome board which we recently went from 32M of SDRAM to 64M, but Linux crashes after it loads the ramdisk image from memory. When Linux is starting, we see "Memory: 64M = 64M total". The SDRAM chips are pin-for-pin compatible (other than the addition of A14).
We are using U-Boot which I changed PHYS_SDRAM_SIZE value from 0x2000000 to 0x4000000. If I leave it at 32M, Linux starts up fine, but it only detects 32M.