As discussed previously, an 8x8 switch is shared by two HBM controllers. Each controller has two pseudo channels, and each pseudo channel has an even and an odd NSU port. The switch connects the eight HBM_NMUs to the eight HBM_NSUs as shown in NoC 8x8 Switch. This allows any input to the switch to reach the entire HBM address space spanning across the two HBM controllers. There are four such 8x8 switches in an HBM stack. There is no horizontal or lateral connection between these four switches. Any lateral connectivity beyond the two HBM controllers sharing the switch is provided by a different switch at the HNoC. There are several basic master-to-slave (HBM_NMU to HBM_NSU) routing use cases in an HBM stack to consider, depending on the application.
|Point to Point (PTP)||A master is accessing the nearest pseudo channel port. This is a 1-to-1 mapping as there is an equal number of master ports and pseudo channel ports.|
|Local Point to Point (PTPL)||A master is accessing a pseudo channel port which is one of the four pseudo channels local to its 8x8 switch instance.|
|Global Point to Point (PTPG)||A master port is accessing a pseudo channel port which resides in another 8x8 switch.|
|Uniform Random (UNR)||A master is accessing all pseudo channels with a uniform random distribution of transaction destinations.|