I port u-boot to magicarm board based on lpc2290, this board has a nor flash whose address range form 0x80000000 to 0x801fffff

ram address(0x81000000-0x817fffff). I modified the micro TEXT_BASE to 0x81080000 and dowmload the u-boot.bin into the flash. the u-boot doesn't work at all . when i modified the micao TEXT_BASE to 0x80000000 and download to flash ,it only work for a while and soon collapsed . who can tell me what the problem is.

this is the ld sccript

OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{
. = 0x80000000;

. = ALIGN(4);
.text      :
{
   cpu/lpc2200/start.o (.text)
   *(.text)
}

. = ALIGN(4);
.rodata : { *(.rodata) }

. = ALIGN(4);
.data : { *(.data) }

. = ALIGN(4);
.got : { *(.got) }

. = .;
__u_boot_cmd_start = .;
.u_boot_cmd : { *(.u_boot_cmd) }
__u_boot_cmd_end = .;

armboot_end_data = .;

. = ALIGN(4);
__bss_start = .;
.bss : { *(.bss) }
_end = .;
}