I’ve just discovered memdisk. It’s part of the syslinux package on Debian/Ubuntu, and hides in /usr/lib/syslinux/memdisk.

Memdisk lets you boot a floppy image, via grub or pxelinux. In this modern era of computers without floppy drives, it means you can do BIOS updates without having to go through the whole procedure of turning a floppy image into a bootable CD.

In PXELINUX, the config file would look like this:

In Grub, like this:

Thanks ThinkWiki for the idea.

Caveat emptor: apparently some flash tools don’t like memdisk, so YMMV