IBM has been the bellwether in mainframe computing for more than 50 years. Today, it continues to lead the way in large-scale design, creating mainframe computers that employ printed circuit boards (PCBs) measuring as large as 50cm x 60cm. Unlike bulky old-fashioned boards, these are enormous configurations of super-miniaturized components. A single board can carry tens of thousands of signal interconnects in more than 10 layers of circuitry. Adding to this complexity, pin counts reach 5,000 per component—with many wide buses connecting them—while at the board level there may be more than 5,000 connections.