The none parameter enables the 7950 XRS-20/20e to use only FP3 cards. This fabric speed is compatible with the following SFMs: sfm-x20, sfm-x20-b, and sfm-x20s-b. When the none parameter is used, there is no fabric speed configured or displayed in the show>chassis output.
The fabric-speed-c parameter enables the use of both FP3- and FP4-based cards and is compatible with sfm2-x20s. For the 7950 XRS-20/20e, the performance of FP3 cards is the same as the none parameter. This fabric speed is displayed as "S4" in the show>chassis output.
If no fabric speed has previously been set on the chassis, the none parameter is set as the default.
The tools>perform>system>set-fabric-speed command is not used in 7950 XRS-40 systems.