Here's the memory map of the low meg on one of my boxes running coreboot:
* 0x00000000 - 0x000003ff Real Mode IVT * 0x00000020 - 0x0000019c MP Table (XXX conflict?) * 0x00000400 - 0x000004ff BDA (somewhat unused) * 0x00000500 - 0x0000052f Moved GDT * 0x00000530 - 0x00000b64 coreboot table * 0x00000c00 - 0x00000c9f SMI communication * 0x0007c000 - 0x0007dfff OS boot sector (unused?) * 0x0007e000 - 0x0007ffff free to use * 0x00080000 - 0x0009fbff usable ram * 0x0009fc00 - 0x0009ffff EBDA (unused at the moment?) * 0x000a0000 - 0x000bffff VGA memory * 0x000c0000 - 0x000cffff VGA option rom * 0x000d0000 - 0x000dffff free for other option roms? * 0x000e0000 - 0x000fffff SeaBIOS? (XXX conflict?) * 0x000f0000 - 0x000f03ff PIRQ table * 0x000f0400 - 0x000f66?? ACPI tables * 0x000f66?? - 0x000f???? DMI tables