These firmware revisions cannot be changed or upgraded by users and cannot be specified when an RMA is created. The differences are done on the design level by the Design Engineers and are not public.
The firmware revision should not effect the performance of the Supervisor modules and having two different firmware revisions in the same chassis should not be an issue. The explanation of the firmware used in the supervisor is given below:
Fw —This is theversion of the firmware installed on the module. Since this is a Supervisor Engine module, the Fw version number is the Network Management Processor (NMP) boot ROM version level.
Fw1 —This is the version of the second firmware image on the module, if present. If this is a Supervisor Engine module, the Fw1 version number is the Master Communication Processor (MCP) boot ROM version level.
Network Management Processor —The NMP on the Supervisor Engine uses system software and performs system control and configuration, including the loading of run-time code to the line modules and system diagnostics. The NMP executes a separate instance of the Spanning Tree Protocol (STP) on each VLAN and runs a wide range of other switch protocols, as well as VLAN Trunking Protocol (VTP), Cisco Discovery Protocol (CDP), and others. The NMP is also responsible for controlling SNMP, Telnet, and console access to the switch.
Master Communication Processor —The primary function of the MCP on the Supervisor Engine is to communicate information between the NMP and the line module communication processors (LCPs) distributed on modules. This intermodule communication occurs across the management bus, which is a serial bus.