VCTlite: Towards an efficient implementation of virtual cut-through switching in on-chip networks

On-chip networks have rapidly emerged as the best interconnection choice for high-core count chip multiprocessors (CMPs) because of the good scalability properties they present. Their fast evolution has been accelerated by the large inheritance from the offchip network domain. Many of the mechanisms and techniques previously developed in that area have been directly applied to the on-chip domain due to the perfect match between the features provided by those techniques and the requirements of on-chip networks. Other mechanisms have been adapted in order to fit the new environment needs. In this paper we present a new example of such an adaptation. Although wormhole switching was initially chosen as the switching mechanism that best fits the on-chip domain characteristics because of its well-known low input buffer requirements, in this paper we show that an efficient implementation of virtual cut-through switching, specially adapted to the particular characteristics of the CMP domain, is feasible as well. Our implementation of virtual cut-through switching, carried out in a 45 nm technology, demonstrates to be faster than a wormhole one, at the same time that does not require more area and reduces power consumption.