e or both of the chassis back- planes. A module that does not support the crossbar fabric is considered nonfabric- enabled. One that supports the 32 Gbps D bus and the fabric bus is considered to be fabric-enabled. A module that uses only the fabric bus and has no connection to the D bus is considered to be fabric-only. Supervisors do not have the same connectors for insertion into the backplane as SFMs. Supervisor-720 modules that include the SFM's functionality have large connectors that can mate only with the receptacles in slots 5 and 6. The connectors for a Sup-720 are shown in Figure 17-5. Figure 17-5. Supervisor-720 connectors Chapter 17: Cisco 6500 Multilayer Switches Nonfabric-enabled modules have connectors on only one side, for connection to the D bus. Modules from a 6000 chassis are nonfabric-enabled, since there is no crossbar fabric bus in the 6000 series. A fabric-enabled module has two connectors on the back of the blade: one for the D bus and one for the crossbar fabric bus. An example of such a blade (in this case, a 16-port gigabit fiber module) is shown in Figure 17-6. Figure 17-6. Fabric-enabled blade connectors Modules that are fabric-only have a single connector on the fabric side, with no con- nector on the D bus side. Be very careful when inserting modules into chassis-based switches such as the 6500 series. Many of the components on the modules are quite tall. As a result, they can impact the chassis and be damaged by improper or forced insertion. Supervisor modules and service modules such as CSMs, ACE modules, and the FWSMs are particularly susceptible to this problem due to the large quantity of components incorporated into these devices. Some of these modules retail for more than $50,000, and you probably don't want to be the one who has to admit to breaking them. Module interaction When fabric-enabled or fabric-only blades are placed in a chassis with nonfabric- enabled blades, the supervisor must make compromises to facilitate the interaction Architecture between the different buse