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As also described by Giuseppe, many of the smaller switches have a one-size fabric bandwidth and forwarding performance; just number of ports wired to it varies per model. Cisco normally documents the capacity of the fabric regardless of the number of ports. Often there might be excess fabric bandwidth that cannot be used on a particular model (or not enough for other models). Cisco also normally documents the PPS, though, at the highest capacity the device can use given its ports, if aggregate performance requirement is less than hardware switching capacity, or total forwarding capacity if the total aggregation of ports can exceed physical switching capacity.
PS:
Requirements for worst-case wire-speed/line-rate Ethernet are: fabric bandwidth = 2 times all port bandwidths (stated non-duplex) and 1.488 Mpps per 1 Gbps of all port bandwidths (stated non-duplex).
