Updated BIOS revisions rewrite the and the PCI-to-DRAM prefetch buffer . A better ROM will allow proper caching of 512MB or 768MB, and properly map the memory to avoid the "PCI hole" at 384MB. This results in noticeably faster load times in Quake III Arena and Unreal Tournament.
The standard bios.rom emulates the older PC-9801 architecture. Adding bios9821.rom upgrades the emulation to PC-9821 standards, which includes support for 256-color graphics , CD-ROM drives, and faster processors. bios9821rom better
