I/O Interfaces & Buses
Why have large SoCs adopted a network-on-chip (NoC) instead of a single shared bus?
- AA NoC enables wireless communication inside the chip
- BA shared bus carries only one transfer at a time, so it congests as blocks multiply and its wires grow long
- CThe CPU cannot read memory over a shared bus
Show answer and explanation
Answer: B. A shared bus carries only one transfer at a time, so it congests as blocks multiply and its wires grow long
A shared bus is enough with few blocks, but with dozens of CPU cores, GPUs and accelerators attached, a bus that carries one transfer at a time becomes congested. A NoC arranges routers and links in a mesh and sends data as packets along chosen routes, so many transfers between distant blocks travel simultaneously. Splitting wires into short segments also makes high clock frequencies easier.
- A. A NoC is also wired.
- B. Correct. A NoC carries many transfers in parallel.
- C. Memory can be read over a shared bus.