Flexibility in ROM: A Stackable Open Source BIOS

One of the last vestiges of closed source proprietary software in current PCs is the PC BIOS. The BIOS, most always written in assembler, operates mostly in 16 bit mode, and provides services that few modern 32 bit operating systems require. Recognizing this, the LinuxBIOS founders began an effort to place a Linux kernel in the ROM of current motherboards- completely removing the legacy BIOS. While the LinuxBIOS effort fully supports Linux, other modern operating systems, e.g. *BSD, and Windows 2000/XP, could not be directly supported because of their reliance on a few services provided by those legacy BIOSes. In this paper, we describe how we have combined elements of the LinuxBIOS, the Bochs PC emulator, and additional software to create the first open source firmware for the IBM PC capable of booting most modern operating systems.