Watch this:
$ qemu-system-x86_64 -nodefaults -vnc :0 -monitor stdio -m 16k
QEMU 1.1.50 monitor - type 'help' for more information
(qemu) qemu: fatal: Trying to execute code outside RAM or ROM at 0x0000000000004000
Admittedly a silly thing to try. I don't really expect SeaBIOS to work
with 16KiB of RAM. But I'm curious: how much does it require?