Increasing 40Gb Ethernet Link Density with the MoSys LineSpeed™ Flex Mux/Demux PHY Device

By Scott Irwin
Vice President, LineSpeed Products
MoSys, Inc.

The MoSys MSH420 and MSH422 devices implement a “Mux/Demux” function which allows two lower-speed serial links to be multiplexed together to form a single link at twice the baud rate.  This “bit-level” Mux/Demux function is agnostic to the data payload of the two lower-speed links, however they must be operating at the same baud rate (i.e., “0 ppm” frequency offset).  Up to 5 bidirectional channels of 2:1 Mux/Demux function are supported in a single device (MSH420).

A prime application utilizing this Mux/Demux function is doubling the port density of 40Gb Ethernet links. A typical implementation carries a 40GbE link across 4 physical lanes, each operating at 10.3125Gb/s. The Mux/Demux allows link transport across only two serial lanes at 20.625Gb/s, as show in the following figure. This can be use in conjunction with either a 40GbE host FPGA/ASIC or with a peer MSH420/MSH422 device to effectively double the 40GbE port density over the same number of pins.

Features and benefits of the MSH420/MSH422 Mux/Demux device include:

The MSH420 and MSH422 devices are the perfect solution for either reducing the number physical links required to transport a given amount of payload or doubling the payload transport for the same number of lanes.

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