Can't find the diagram I'm looking for, but recall the 3560/3750 split the ports across 2 or 3 internal ASICs. Each port, I think, including the SFP ports, has gig but there is an oversubscription of the ports per ASIC and internal fabric.
From http://www.cisco.com/en/US/products/hw/switches/ps5023/products_qanda_item09186a00801b0971.shtml
Q. Are the Cisco Catalyst 3750G 48-port units oversubscribed?
A. Yes. There's a 52 to 32 Gbps oversubscription.
Q. What is the difference between the 3560G and the 3750G?
A. The 3560G SKUs are the standalone versions of 3750G. The 3560G SKUs do not implement the Cisco StackWise technology found on the Cisco Catalyst 3750 Series.
Q. What is the difference between the 4948G, 3750G, and 3560G 48 port units?
A. The 4948G is a full wire-rate box with a 96 Gbps, non-blocking, full-duplex switching fabric based on the Cisco Catalyst 4500 K-2 architecture, providing 72 million packets-per-second of switching capacity. It has removable redundant power supplies and a removable automatic variable speed fan tray. The 4948G series is also available with DC power supplies which aren't available on most 3750 or 3560 SKU's. The 3750G and 3560G 48 port units have oversubscribed switching backplane (52-to-32 Gbps oversubscription) and only have 1 power supply and fixed fan units. The 3750G units can stack together with other Cisco Catalyst 3750 Series or 3750G units using StackWise technology to form a single virtual switching unit. The 3560G is a standalone switch.
