Traditional Bus Architecture

Figure shows some typical example of I/O devices that might be attached to expansion devices The traditional bus connection uses three buses local bus , system bus and expansion bus

1. Local bus connects the processor to cache memory and may support one or more local devices

2. The cache memory controller connects the cache to local bus and to the system bus.

3. System bus also connects main memory module

4. Input /output transfer to and from the main memory across the system bus do not interface with the processor activity because process accesses cache memory.

5. It is possible to connect I/O controllers directly on to the system bus. A more efficient solution is to make use of one or more expansion buses for this purpose.An expansion bus interface buffers data transfer between system bus and i/o controller on the expansion bus.

This arrangement allows the system to support a wide variety of i/o devices and at the same time insulate memory to process or traffic from i/o traffic.