I use VirtualBox to run Windows to prepare Windows-only BIOS updates for customer computers, especially since floppy disks are so rare now.
Make a folder to work in:
mkdir CD
In the Mac OS Terminal, create an empty floppy disk image:
dd if=/dev/zero of=CD/bios.img bs=10k count=144
Attach it as a floppy image in Virtualbox running Windows. Run the BIOS update disk creator in Windows.
Detach the floppy image, then create a CD image with the bootable disk image:
hdiutil makehybrid -o boot.iso -joliet -iso -eltorito-boot CD/boot.img CD
Then burn the CD:
hdiutil burn boot.iso