Author: Rachelle Trent
PMC-Sierra, Inc.
The migration from parallel to serial interfaces is not a new idea to enterprise and storage applications. These storage interface technologies have turned to a serial approach because parallel implementations have become a performance bottleneck.
Parallel buses suffer from many undesired analog effects such as crosstalk, ground bounce, ringing/reflections and clock skew. Pushing parallel technologies to higher and higher speeds intensifies these analog symptoms and places major constraints on designs that must maintain backwards compatibility to legacy parallel technology.
The new standard, Serial Attached SCSI (SAS), is the evolution of the SCSI interface from a 16-bit parallel bus approach (Ultra320 SCSI) to a differential serial link running at 3.0 Gb/s. SAS is being introduced at 3.0 Gb/s and has a planned roadmap up to 12 Gb/s over the next several years.
