The RCube [4] is an 8x8 router for IEEE 1355 HS-Link networks. Its is based on an 8x8 non-blocking crossbar switch and 8 bidirectional 1 GBaud serial links. This results in a total cross-sectional data bandwidth of 640 Mbyte/s. The RCube uses ``Wormhole Routing'' [5], which allows packets of unlimited length to be routed. It also provides very low latency in lightly loaded networks, each RCube has a latency of only 150 ns. The device also provides adaptive routing which enables efficient load balancing in multistage networks, as demonstrated for the DS-Link technology [6].
Figure 3 shows a block diagram of the RCube. The chip is built from three different functional units. The High Speed Link macrocell includes the serialiser/deserialiser and provides the interface to the HS-Link. The Serial Macrocell Interface provides the character coding/encoding along with the link boot protocol and interfaces between the HS-Link macrocells and the router core. The parallel router core (R3P) operates with a character wide data path.
Figure 3: Block diagram of the RCube router
Two of the HS-Link interfaces can be bypassed, which allows for character wide parallel access to the router. This was implemented for device testing, but can also be used as a parallel interface to an HS-Link network. The parallel interface of the RCube does however not have the simple FIFO interface of the Bullit chip and requires careful design of the interface logic if this feature is to be used.