If I use a default config for i440fx/piix4, building a 16MB ROM works fine, but 32MB or 64MB doesn't work anymore:
... CC postcar/southbridge/intel/common/rtc.o LINK cbfs/fallback/postcar.debug OBJCOPY cbfs/fallback/romstage.elf CREATE build/mainboard/emulation/qemu-i440fx/cbfs-file.vqaXlP.out (from /home/my_custom_path_to/coreboot/.config) CC+STRIP src/lib/cbfs_master_header.c OBJCOPY cbfs/fallback/bootblock.elf OBJCOPY bootblock.raw.elf OBJCOPY bootblock.raw.bin Created CBFS (capacity = 33553892 bytes) BOOTBLOCK CBFS cbfs_master_header CBFS fallback/romstage cbfstool: /home/my_custom_path_to/coreboot/util/cbfstool/cbfstool.c:1145: cbfstool_convert_mkstage: Assertion `IS_HOST_SPACE_ADDRESS(host_space_address)' failed. make: *** [Makefile.inc:1116: build/coreboot.pre] Aborted