IBM PC AT BIOS dated 06/10/85 based on the BIOS listings in the IBM PC AT Technical Reference dated September 1985.
The BIOS was originally built using IBM MASM 2.0.

Notes:
- FILL.ASM was added to properly link the BIOS, this defines the area between the end of the main BIOS code and the ORGS data at E000.
- IAPX286.INC was derived based upon the generated code in the listings.
- In TEST1.ASM there is an invalid POP instruction with no operands which MASM 2.0 assembles as PUSH 0.
- The code at FF5A in ORGS.ASM is hidden from the BIOS listings with .XLIST.

Additional files:
FILL.ASM - see above
ATLINK - linker response file
EXE2BIN - DEBUG script to convert the EXE file to a BIN file

Steps to build the PC AT BIOS:
for %a in (*.asm) do masm %a;
link @atlink
debug < exe2bin