I need to build a bootable ISO image I can run DOS programs from. As part of the creation, I'll need to get a 9 MB BIOS update on that ISO so I can flash my motherboard.

Google searches turn up lots of misinformation that make too many assumptions that you have a "boot.img" and junk like that already. I need to understand the procedure top to bottom.

How do you tackle this?

http://www.linuxfromscratch.org.

Prepare for an adventure.

Tackle what exactly? you said that want to make a "bootable ISO image I can run DOS programs from" ... which i'm afraid doesn't make much sense. (what do DOS programs have to do with linux??)
but since you're posting in a linux forum i guess you're asking how to make a linux distribution or at least a minimal LINUX boot image ...etc

well, it all starts with compiling the kernel (obviously) , then figuring out how to boot it using a bootloader such as grub or lilo (or compiling a bootloader from source then use it to boot the kernel which way ever).
unfortunately the kernel alone doesn't do anything , so you need a C library (which servers as a mediator between the kernel and whatever apps you're trying to run aka userspace programs) such as glibc.
depending on whether you're building your boot image for the same architecture you're intending to run it for , you may need to build a toolchain (not needed if for same arch) which involves building 3 primary components binutils,gcc,glibc and other secondary ones several times in a pre-determined order hence the name. (needless to say this is complicated !!)

if you've reached this stage you can , compile/add all the applications you need in your boot image , which at this time would be chrooted directory on your hdd or something similar.
finally , you can use various command-line tools such as "mkimage" found in grub in order to create an ISO image out of this directory. (the irony is that creating the final ISO image is the most trivial part)

i guess you mean bottom up , because you won't get the top if you don't know about the bottom !

P.S check out "linuxfromscratch" , "building a toolchain" , "compiling the linux kernel" , "bootloader"..etc

Good Luck

bootable iso that can run dos program, try freedos live cd

to understand the procedure to create bootable iso image, please check slitaz scratchbook

HTH

Hopefully this clarifies more: Use Linux tools to create media that works on Windows systems. ??

I found isomaster which lets me use an image of the boot sector (that I extracted by other tools) and build it into an ISO project. Then I put my BIOS update EXE and BIN as part of the data are in the ISO project. But there seems to be some missing magic that ties the boot sector to the added files. E.g. the resulting ISO boots, but the binaries are invisible when typing "dir".

If you have a boot image you might just be able to use it as track one on the cd.

I used to use cat to get an image of a dos floppy. Then take that file and burn it using nero with a cue sheet. I didn't have linux at the time but the posts said to just use track one. The track two could be the file you need. It ought to then show up as b drive.
A floppy to track one ought to show as a.


I agree that freedos may be the correct choice. It can use usb to access this file.