The RB493 has nine ethernet ports and three miniPCI slots, it also has a switch chip, so the ethernet ports 2-9 can be grouped together to make it act as a switch. 
RB493 includes RouterOS - the operating system, which will turn this powerful system into a highly sophisticated router, firewall or bandwidth manager. 
With nine Ethernet ports, and three miniPCI slots, this is our most versatile RouterBOARD model. 
The RB493AH model includes the higher speed Atheros 680MHz CPU, more memory, and a Level5 license for more simultaneous tunnel interfaces and hotspot users.

Product specifications

Throughput results

1. Notes:
2. All throughput tests done with Xena Networks specialized test system and RouterOS v5, according RFC2544, with Ethernet frame sizes 64, 512, 1518 bytes.
   Each board is tested with specified number of Ethernet interfaces, to ensure optimal load on hardware.
3. Values in Italics indicate that the maximum possible throughput was reached, limited only by ethernet ports themselves.
4. http://routerboard.com/pdf/84/rb493AH.pdf