[coreboot] coreboot generated .rom is not bootable. why?

[유택연]

I followed instruction from http://www.coreboot.org/AMD_SimNow .
All compilation was done with no error.
But SimNow not accept my coreboot.rom.

The error message is

BIOS ROM file is the wrong size for this BSD.  Please either point the
memdevice to the correct BIOS ROM file, or configure the memdevice to be the
correct size.

I suposed this error was caused by header mismatch.
Generic ROM file has '0xaa 0xbb 0xcc 0xdd' signature at address 0x00000000.
But coreboot.rom does not.

On real machine which has coreboot.rom flashed, stopped BIOS loading after
first access.

How do I get a correct coreboot.rom?