17
Interconnection Networks in Network-on-Chip
Figure 2.4
A 4 × 4 2D folded torus with single core connected to each router.
for implementing the CMESH network is one-fourth of that of a traditional mesh structure as shown in Figure 2.5. To make the bisection width
same as that of the mesh structure, additional long interconnection links
are attached along the perimeter of the network. The node degree of each
router in the CMESH network is 8, much higher than in the mesh, torus,
and folded structures. A CMESH network having M × N IP blocks has the
following parameters:
Diameter: (M/2 + N/2 − 4)
Bisection width: min [{(M/2 + (2 × ⎢ ⎣ (log 2 N) − 1⎥ ⎦ )}, {N/2 + (2 × ⎢
⎣ (log 2 M) − 1⎥ ⎦ )}]
Number of routers required: (M × N)/4
Another interesting network is the octagon structure, in which connection
between any two nodes (within an octagon subnetwork of eight nodes)
requires at most two hops (Karim et  al. 2002). Each node in this network
is associated with an IP and a switch as shown in Figure  2.6. For embedding more than eight processors, more octagons can be combined together
by using bridge nodes. For a system consisting of more than eight nodes,