For decades, parallel bus architectures have been the most common means of transporting digital signals around a system. Now that system data rates have accelerated into the gigabits-per-second range, narrow serialized buses have emerged to take the place of wide parallel architectures. What was once a 128-bit parallel connection might become, for example, a four-line serial bus. These few physical lines must carry the same amount data as their parallel counterparts―or more. Current and emerging serial bus standards include Serial ATA, USB 2.0, Hypertransport, as well as a new generation of serial "fabric" bus architectures including Infini-band and RapidIO (see Fig. 1). The benefits of serial bus design are substantial.
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