An 8x8 switch is shared by two HBM Controllers. HBM Controllers are split into two pseudo channels, each with two NSU ports. The 8x8 switch can route HNoC packets to either Pseudo channel of either HBM Controller. If a packet needs to reach an HBM Controller outside of the pair, it would be routed to a different switch at the HNoC. There are no connections between 8x8 switches.
The following figure shows eight inputs to the switch, an ‘even’ denoted by a solid arrow, and an ‘odd’ denoted by the dotted arrow. The switch can route any even input to a solid arrow output, and similarly for the odd inputs. This allows any input to the switch to reach the HBM address space spanned by four pseudo channels. Two NSU ports to each pseudo channel ensures sufficient bandwidth to fully utilize the HBM throughput.