m0n0wall will run on any standard x86 PC that supports at least two network interfaces.
486 processor - Any 486 or higher processor is sufficient for m0n0wall. Exactly how much processor you will need for your particular implementation varies depending on your Internet connection bandwidth, number of simultaneous connections required, what features you will use, etc. For most deployments, a 486 or Pentium processor is sufficient.
64 MB of RAM - 64 MB RAM is the official suggested minimum. The CD version of m0n0wall has been reported to work fine for some people with only 32 MB. When using the CompactFlash or hard drive versions of m0n0wall, expect upgrades to fail with less than 64 MB. This is because m0n0wall stores everything in RAM and uses no swap space - when it runs out of RAM, it has nothing to fall back on.
There are some BIOS settings that may need to be changed for m0n0wall to function properly.
Plug and Play OS
Most system BIOS have a setting for "Plug and Play OS" or something similar. This should always be set to "no" or "disable". With this setting turned off, the BIOS assigns system resources rather than leaving that up to the OS. FreeBSD (and hence m0n0wall) works best when the BIOS handles this task.
Disabling Unnecessary Devices
You most likely won't have to worry about this, but if you have hardware-related issues, we recommend disabling all unnecessary devices in the BIOS, such as onboard sound, and in some cases parallel ports, serial ports, and other unused devices. If you aren't using it, it is safe to disable it.
m0n0wall will run off of a CompactFlash card, hard drive, or CD with floppy to store the configuration.
At least an 8 MB CompactFlash card is required.
Any IDE or SCSI (with supported controller) hard drive will work fine with m0n0wall.
Any IDE or SCSI (with supported controller) CD-ROM or DVD drive will work with m0n0wall. Also required for this setup is a 1.44 MB floppy drive with blank floppy disk formatted with MS-DOS/FAT file system. Any standard floppy drive will work. For this setup, you must have a PC that supports booting from CD-ROM.
Zip drive setup
Starting with 1.2b3, m0n0wall can run the hard drive image from a Zip drive. Write the disk the same way you would write a hard drive.