What is the advantage of using multiple routers?

[mubashir913]

I have a question regarding routers. If I want to have for example 5 chimneys, is there some advantage of connecting each chimney to a separate router over connecting all the chimneys to a single router? Because when using multiple routers like in a mesh, it takes more cycles for a transaction to complete between two chimneys connected on first and last router. Why can't we just always connect all the required chimneys to a single router?

[fischeti]

You can definitely do that to decrease latency, but whether that makes sense depends on the number of links you attach to a single router. A router scales quadratically with the number of links, so at some point, a single all-to-all router is not feasible anymore (this is why NoCs were introduced in the first place).

Also, If you have a smaller system an all-to-all interconnect is still feasible, a NoC doesn't really make sense in the first place. You could also just use normal AXI Xbars.

There is also a an example configuration, which uses a single router with a couple of endpoints

[mubashir913]

Thank you so much for answering my question.

[mubashir913]

I have a question about the router links. A chimney is connected to a router through 6 channels (req, rsp, & wide input and output). Are these 6 channels considered 6 links, or are they considered as a single link?

[fischeti]

They are separate links i.e. every link has its own router