The DMA engine in the PLX devices can also be used to perform the multicast function. The advantages for implementing a DMA-based multicast scheme include support for an unlimited number of multicast groups (each descriptor ring represents a multicast group), a reliable multicast scheme (status for each copy made can be provided by a DMA engine), that multicast transfers are not limited to posted transactions, and most importantly, DMA-based multicast from PLX provides a PCIe multicast solution today.
The addition of multicast in PCIe devices is being addressed today within the PCI Special Interest Group (PCI-SIG®) in the form of an engineering change notice (ECN) to the PCIe 2.0 specification. The ECN describes the function of multicast, which enables the PCIe switch to send a single packet to many destinations simultaneously, thus dramatically reducing latency and increasing the effective throughput of a system.
Processor and chipset makers have been implementing DMA as part of their efforts to increase system performance for years in markets such as embedded control planes, enterprise storage and computing, said Sergis Mushell, principal research analyst, Gartner Research. Dynamic memory access technology has proven itself and the integrated PLX solution within the PCI Express switch should find wide acceptance in the design community.
PLX Technology Inc.