Cisco 7200 VXR routers also support the NSE-1, which consists of two modular boards: the processor engine board and the network controller board. The NSE-1 Parallel eXpress Forwarding (PXF) processor works with the routing processor to provide accelerated packet switching, as well as accelerated IP Layer 3 feature processing.The NPE-100 has an R4700 microprocessor that operates at an internal clock speed of 150 MHz. The NPE-100 has a system controller that uses direct memory access (DMA) to transfer data between DRAM and packet SRAM on the network-processing engine. The NPE-100 uses DRAM for storing routing tables, network accounting applications, packets of information in preparation for process switching. The NPE-100 has unified cache SRAM that functions as the secondary cache for the microprocessor. (The primary cache is within the microprocessor.)