Three emerging chip-to-chip interconnections: HyperTransport, PCI Express, and RapidIO are being increasingly integrated into semiconductors and systems, and shipments bearing these technologies will grow over the next several years, reports In-Stat. PCI Express will experience the highest growth of all three interconnects rising from 8.7 mln systems in 2004 to 283 mln in 2009. Despite shrinking use in consumer applications, In-Stat is forecasting a 28% CAGR in the use of HyperTransport fueled by its success in computing and routing applications. RapidIO is clearly a distant third in I/O wins; however, it has found a defensible position in telecommunications. Although each interconnect has roadmaps to higher speeds and bandwidth, each faces challenges overcoming jitter using current circuit board technology. These challenges may eventually force a transition to optical interfaces.