You can create a ms-dos floppy disk, maybe "format /mbr"? Forgot now how to insert a boot sector in a formated disk, it's necessary copy command.com, config.sys and autoexec.bat and update bios software. After a bootable disk (cd-rom,pen-drive, floppy) thats easy, from memory I remember that update bios program give to us an option to save actual firmware bios image to disk as file. Maybe ramdisk.sys can be usefull to create a file system in memory. So, after bootup is necessary format again just to store bios image.
Have other ways, but you need 2 same motherboard (bios chip). You turn on computer with good bios image and save to a file; after this and while computer on, remove very carefully the bios chip with good image inside and insert a bad bios chip; after this you can update bad bios chip image while program is waiting us to press a key to update bios image. I have done this a lot in past when finding bios image was hard. Other option was eprom writer, but thats specific to electronic persons.
Ms-dos and bios image are stored in memory (int 21 by command.com and int16,int10 from bios image).
One problem happened to me while updating a bios image was a energy peak. That create a bad bios image, computer just don't turn on. So, if it's raining, better do this after.
Maybe, not sure, but motherboard cd-rom are bootable.
