PMON is a freeware ROM-monitor developed for early LSI Logic MIPS R3000 evaluation boards. Since its creation, PMON has become a very common firmware for MIPS evaluation boards and development systems.
For old information on PMON, visit Phil Bunce's (PMON's designer) website at http://www.carmel.com/pmon . The site has not been updated since 2002 and the code is from 1999.
The original PMON code base is rather old now, supports relatively few boards and is not being actively worked on by a single project team. PMON 2000 has become the unofficial successor of PMON. This code is also old. The latest tarball is from the 2002/2003 timeframe. The page claims CVS access is available but non-ssh connections are refused and the required ssh private key for the CVS server is nowhere to be found at the site.
PMON comes with excellent documentation in HTML.
The latest PMON source, modifyed by Algorithmics is available as pmonsrc-20011116.tar.gz. It contains support for much more boards, R4000-style exeptions, and comes with more recent build system (for GNU make).
Linksys WRT54G and Asus WL-300g, a WiFi 802.11g AccessPoint (both BCM47XX based) use PMON version 5.3.22 as a Linux bootloader. PMON ported to the BCM47XX is available from the GPL'ed sourcecode for these devices.