The black key on the bottom left was used to open the side panels of an Amdahl 580 and jerryd6818 will tell you that the chips were mounted in an 11-by-11 array on multi-layer boards called Multi-Chip Carriers (MCCs) that were positioned in high-airflow for cooling. The MCCs were mounted horizontally in a large rectangular frame. The MCCs slid into a complex physical connection system. The processor "side panels" interconnected the system, providing clock propagation delays that maintained race-free synchronous operation at relatively high clock frequencies (15–18 ns base clock cycles). This processor box was cooled by high-speed fans generating horizontal air flow across the MCCs.
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