As can be seen from the number of options described above, the Ethernet complexity and variations are numerous. For example, for a 51.2T Ethernet switch running at 100 Gbps line rate, we find that Ethernet could be implemented in at least three different configurations, as shown in Figure 3.
Configuration 1 - Monolithic Topology: This is 512 lanes of 100G SerDes placed on all edges of a single monolithic die, implemented with 128 instances of x4 112G Long Reach (LR) SerDes coupled with a Quad or Octal PCS & MAC . Factors to consider are available beachfront and floorplanning to ensure optimal routing, MAC/PCS placements and overall timing feasibility.
Configuration 2 - Two-Die Topology: This is a two-die implementation, connected by 112G Extra Short Reach (XSR) SerDes. Each implementation includes 64 instances in a x4 112G LR SerDes and Quad or Octal PCS & MAC. Advantages of a multi-die implementation are increased beachfront and better yield from each smaller die vs. a monolithic die.
Configuration 3 - Companion Die Topology: This is instances of 112G XSR on the host side connected to eight companion dies on the line side. Each companion die consists of 16 instances of x4 112G LR SerDes and Quad or Octal PCS & MAC. The advantage is that the main die can be in a more aggressive process node while the companion die could stay in older and more mature processes.