next up previous

Exercise 19: A consideration of some of the communication that takes place on a KSR-1.

The ring network in the KSR-1 is a slotted ring, which means packets flow around the ring in discrete steps under control of a global clock. The KSR-1 transfers 128 million packets per second past each slot on the ring.

(a) The bandwidth is 1GB/sec. How wide is the communication channel?

(b) The processor cycle time is 20MHz. How many packets can be taken off the ring during each processor cycle?

(c) What is the diameter of a full-size (1088-PE) KSR-1?

(d) Ignoring communication overhead and the possibility of contention that would delay a message, how long will it take the machine to transfer 256 bytes along the longest communication path?