Some of these firmware files are property of someone else; probably LEGO, Inc. or Dick Swan.

They are provided here as a convenience only, as they can be found all over the internet.

Note that it is unknown if any of the "fast" firmwares work with any current version of NQC, as I only test with LEGO firmwares.

firm0309 - Original version shipped with RIS 1.0 and 1.5
firm0328 - Shipped with RIS 2.0
firm0332 - Released as part of the LEGO Education Robotics sets
fast0103 - Dick Swan's 10x firmware; compatible with most bricks and NQC
fast0612 - Dick Swan's 100x firmware; mostly compatible with NQC 3.1r5
fast0722 - Dick Swan firmware that only works with RobotC
fast0753 - Dick Swan firmware that only works with RobotC
fast0798 - Dick Swan firmware included with the last version of RobotC
           for the RCX

Unless there is a compelling reason not to do so, you should just use the latest LEGO firmware (0332) for NQC, which can be used in any RCX brick from 1.0 on.