Peter will correct me if I'm wrong here, but the word on the street was that when the new "flagship" Cisco 7000 was introduced, its routing performance was lackluster compared to a well-configured AGS+, which caused some issues with 7000 adoption. Later 7000-family hardware enhancements corrected those performance issues. A cisco 7000 (router) is a AGS+ with Cbus2 painted green..... The SC is a Cbus controller and it still has a multibus. Tony's silicon switch engine is a trinary-tree-host-route lookup engine with packet buffer that replaced the SC.. In 7500 the multibus was finally gone. It still has the Cbus chanel structure now renabed to CX and later CY bus but now the buffer and switching is done on the CPU named RSP.. The Mips R4000 is doing packet switching with a hand-written code path on the 7500.. Packets go across the cbus/cxbus twice, in and out and the DMA engine is on the linecards. The buffer memory is named "memd" and the 12000 is a bigger 7500 with a switch, but it still has "memd" on the RP to porcess packets to/from the box itself... -P