
458 CHAPTER 12 Networks-On-Chip
between the sender and receiver. Since credit traffi c can consume a large chunk of
the NoC bandwidth, the requested credit packets can be combined with response
packets, and vice versa. This is known as piggy backing [29], and is a common tech-
nique to save bandwidth. The Æthereal [15] and QNoC [30] architectures make
use of end-to-end credit-based fl ow control. Nostrum [5] has also been extended
to use the same fl ow control scheme. This credit-based fl ow control scheme can
be applied at the link-to-link level as well. Typically, link-to-link credit-based fl ow
control is used with virtual circuit switching, where ...