First off, this was way more trouble than it was worth. But it seems to be working.
I'm posting this in case anyone else is thinking of trying to run m0n0wall on an old Watchguard Firebox III. I got a decomissioned FB 700, but I think the basic system is the same with all the Series III boxes- 700, 1000, 2500, 4500. The differences were the processor speed, memory, and if the PCI slot was exposed.
The FB II guide was helpful for hardware tips:
http://www.ls-net.com/m0n0wall-watchguard/The FB III uses an AMD K6-2/3 and laptop sd-100 ram. I pulled the board, put a video card in, upgraded the ram to 128, and the processor to 500 (from the junk bin). Eventually got a keyboard wired up.
My initial thought was to run pfSense off a laptop HDD on this thing, but I could not get it to boot sucessfully. Stock 6.2, 6.3, or 7.0 would not run either.
I came across this, which seemed to confirm the hardware was funky:
http://lists.freebsd.org/pipermail/freebsd-drivers/2008-February/000601.htmlLater I stumbled across the follow up where Kazuhiro Sakai tells how he got m0n0 running on the FB III, complete with his patches to source:
http://www.nabble.com/Re:-Running-FreeBSD-on-Firebox-III-td15789848.htmlExcellent. I dug out an old 4.11 disk, installed on a laptop drive from another PC (using an adapter), clumsily patched the sources, applied the m0n0wall 4.11 kernel patches, and built a custom kernel. I moved the laptop drive to the FB and found it fully booted!
Then, I DD'd the net45xx image of 1.234 (generic pc didn't give me a serial console) to the built-in flash (having used to jumper to wipe it). After that, I deleted the stock kernel off the flash, and copied in the hand-rolled one. The crappy NICs don't auto-sense (perhaps due to the hack to make the MAC address stick). But hacking the config allowed me to get the system running. Again, it would have been better if I had just smashed the box with a large hammer due to the time wasted, but it is kind of cool to have the thing running m0no off the flash.