Cisco 7206VXR routers accommodate a variety of network interface port adapters and an Input/Output controller. A Cisco 7206VXR NPE-G1 supports up to six high-speed port adapters and higher-speed port adapter interfaces including Gigabit Ethernet and OC-12 ATM. Cisco 7206VXR routers accommodate up to two AC-input or DC-input power supplies. The NPE-G1 uses an RM7000 microprocessor that operates at an internal clock speed of 350 MHz. The NPE-G1 uses SDRAM for storing all packets received or sent from network interfaces. The SDRAM memory array in the system allows concurrent access by port adapters and the processor. The NPE-G1 has three levels of cache: a primary and a secondary cache that are internal to the microprocessor, and a tertiary 4-MB external cache that provides additional high-speed storage for data and instructions.