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

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

Flat assembler syntax.
Pure 8086 code.
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. Concatenate loader and the ROM image, write into floppy.
Makefile will prepare 5.25" 360K/1.2M and 3.5" 720K/1.44M floppy images.
MIT License. See LICENSE file.

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:
  - 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.

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

Roc Vallès Domènech

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

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