les. It is for this reason that the speed of a 6500 can change with a new supervisor module. Figure 17-3 shows a visual representation of the backplane in a 6509 chassis. Look- ing at the chassis from the front, you would see each slot's connectors as shown. There are two backplane circuit boards separated by a vertical space. To the left of the space (at the back of the chassis) are the power connectors and the crossbar fab- ric bus. To the right of the space are the D, R, and C buses. A 6000 chassis would look the same to the right of the space, but have no crossbar fabric bus to the left. Chapter 17: Cisco 6500 Multilayer Switches D Bus - EARL data bus Crossbar R Bus - EARL results bus switching C Bus - Control Bus or Ethernet Out Of Band Channel (EOBC) Power fabric D R C Slot 1 - Supervisor (I, la, II, 32), Line card or Module Slot 2 - Redundant Supervisor (I, la, II, 32), Line card or Module Slot 3 - Line card or Module Slot 4 - Line card or Module Slot 5 - Supervisor (720), Switch Fabric Module, Line card or Module Slot 6 - Redundant Supervisor (720), Redundant Switch Fabric Module, Line card or Module Slot 7 - Line card or Module Slot 8 - Line card or Module Slot 9 - Line card or Module Figure 17-3. Cisco 6509 backplanes Certain slots are capable of taking specific modules, while other slots are not. The breakdown of slots in a 6509 is as follows: Slot 1 Slot 1 is capable of housing supervisor modules 1, 1A, and 2; line cards; or ser- vice modules. If there is only one Sup-1, Sup-1A, or Sup-2 in the chassis, it should reside in slot 1. Slot 2 Slot 2 is capable of housing supervisor modules 1, 1A, and 2; line cards; or ser- vice modules. This slot is used for the redundant supervisor module if a failover pair is installed. Though a single supervisor can be installed in this slot, the first slot is generally used for single-supervisor installations. Slot 3 Slot 3 is capable of housing any line card or module, with the exception supervisors or SFMs. Slot 4 Slot 4 is capable of housing any line card or module,