optromloader: IBM PC/Clone 8086+ floppy-loading of option roms.

Booted from a floppy, it will load an Option ROM image into the top of conventional memory.

Use cases (non-exhaustive)

• Test boot ROMs before burning them.
• Netboot with etherboot/gpxe/ipxe.
• IDE support (including LBA!) with XTIDE Universal BIOS.

Highlights

• Flat assembler syntax.
• Pure 8086 code.
• Single stage. (Fits in a floppy bootblock)
• Verifies ROM image checksum after loading.
• Supports all Option ROM sizes. Spec goes up to 127.5KB, but full 128KB ROMs are supported.
  • An extra block is read when length=255 (127.5KB/128KB case).
• Reserves memory from top of conventional memory.
  • Alternatively allows specifying target segment (upper area possible).
• Works on PC/XT/AT and clones.
  • Also works on newer hardware, such as the 486 with AMI BIOS I wrote it for.
• Trivial to use.
• Makefile will prepare 5.25" 360K/1.2M and 3.5" 720K/1.44M floppy images.
• MIT License. See LICENSE file.

Usage

• Ensure fasm (flat assembler) is installed.
• Copy your ROM image as the optrom.bin file.
  • Ensure the ROM image is signed (has correct checksum).
    • optromloader will loudly refuse to run the ROM image if not signed.
    • Test with make emulaterom. Qemu's BIOS won't see the ROM if it's not signed.
    • Qemu provides a python tool to sign ROMs:
      • https://github.com/qemu/qemu/blob/master/scripts/signrom.py
    • For XTIDE Universal BIOS ROMs, use its XTIDECFG tool to configure and sign ROM images.
• Optionally review Makefile for advanced usage.
  • If boot floppy drive won't be A:, set bios_drive value appropriately.
  • If specifying target segment in upper memory, ensure it is visible as memory in BIOS settings.
    • into-486 works on my AMI BIOS 486.
• Run make.
• Floppy images will be created (fd*.img).
• Optionally test 1.44M image with qemu: make emulate.
• Alternatively, use a binary release. Concatenate:
  • optromloader9/15/18, according to sectors per track in your floppy format:
    • 9 for 5.25" 360K and 3.5" 720K.
    • 15 for 5.25" 1.2M.
    • 18 for 3.5" 1.44M.
  • the ROM image.
  • pad to floppy size.

Caveats

• Option ROMs that make assumptions about their base address may not work if loaded into a different address.

Author

Roc Vallès Domènech