x86 embedded BIOS R3

Very compact (less than 8KB of ROM space) x86 BIOS for embedded systems, FPGA, and emulators.

Tested with a hardware:

• Original Intel 8086 CPU
• Harris 80286 CPU
• Intel 80386SX25 CPU
• Intel KU80386EX25 CPU
• Cyrix Cx486SLC-V25 CPU
• Texas Instruments TI486SXLC2-G50 CPU

Some board images could be found in the pictures directory.

Tested with an emulators:

• Bochs 2.6.11 (require USE_ADDON_ROMS and USE_IDE_HDD in "config.inc" to use Bochs's Video BIOS and HDD)

Tested with a software:

• MS-DOS 3.3, 4.0, 6.22
• Windows 1.0, 2.0, 3.1, 95
• Linux 0.01, 1.3.89
• Minix 1.x, 2.x
• Most of DOS/Windows software and games working good

Compiling on Windows machine

• Use Netwide Assembler (https://www.nasm.us/) to compile the source code.
• Edit "config.inc" file to select features you need.
• Launch "_make.bat" file to create binaries.

If your NASM location on disk is not "C:\nasm\nasm.exe" - please change the path to nasm.exe in "_make.bat" file.

Implemented functions and features

• Minimal initialization
• Minimal functionality ISRs 10h-1Ah
• Lower memory test with continuous mode to help debugging FPGA SDRAM controller
• Very compact Video BIOS
• Minimal SVGA functionality enough to run hi-res games like "Heroes Of Might and Magic" and "Transport Tycoon"
• Supports add-on ROM chips (see config.inc)
• BIOS disk hypercall for emulators
• SPI mode SD-card support on FPGA boards
• Very simplified USB HID device support for FPGA boards
• Good for a systems without video adapter
• Customizable SPI/USB drivers
• A20 line and PLL control (frequency multiplier for 486)

Known issues

• No hardware detection / BIOS setup (to save ROM space)
• No extended memory test
• Int 13h (BIOS disk) supports only reset/read/write functions
• Internal video BIOS doesn't support printing text in graphic mode
• Video adapter initialization incomplete so will not work properly with a real VGA chips without OEM BIOS

Disclaimer

The project is provided "as is" without any warranty. Use at your own risk.

Please contact me if you find any bug or if you plan to use it with a physical hardware.