Building a boot floppy for BIOS flashing

May 11, 2006

Part of today was arranging to flash a new BIOS on my new machine here (in the hopes that the most recent BIOS version would fix a mysterious memory corruption problem). This was a bunch of annoyance, because I had to come up with a bootable MS-DOS floppy to run Tyan's BIOS flasher program from. So that I don't have to go through all the work next time around, I'm going to put what I found here.

In the old days, it was simple: I'd go ask someone running Windows 95 or 98 to make me a boot floppy, slap the flash update program on it, and go. Unfortunately, no one around here is running those Windows versions any more and apparently newer versions can't do this any more. (Since Windows is no longer based on MS-DOS, this isn't too surprising.)

What you really need is a bootable DOS floppy image that you can just dump onto a floppy. What I used is the FreeDOS image from Flashing BIOSes; the actual article is mostly about making bootable CD-ROMs for BIOS flashing. (When booted the image will offer you a bunch of options for what next; pick 'clean boot'. There's probably some way to set it to boot straight to the old-style DOS prompt, but I didn't poke around.)

There's also HOWTO Create a DOS boot disk (and here), from the Gentoo wiki. The FreeDOS images they use seem to be more minimalistic than the Flashing BIOSes ones.

Other approaches and more information

There's a number of places with actual MS-DOS boot images (copyright Microsoft and all), like here or here, but they tend to have them wrapped up in DOS .exe files and other odd formats instead of being in nice dd-able images. And of course they're almost certainly being distributed without Microsoft's permission.

Flashing PC BIOS under Unix/Linux in non-traumatic fashion has one of these in a convenient for Linux format, and instructions as well.

If you don't want to bother with the mess of an actual floppy and already have a working Linux installation, look at memdisk. Memdisk will boot a floppy image from memory, without the mess of a physical floppy. The drawback of this is that you can't save the old BIOS image if your BIOS flashing program offers this option.

(While SYSLINUX can make a bootable floppy it doesn't include a MS-DOS compatible command.com et al, without which you can't run the BIOS update utilities.)

Written on 11 May 2006.
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Last modified: Thu May 11 02:36:39 2006
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