SISD (Single instruction single data stream) is the simplest computer available. It contains no parallelism. It has single instruction and single data stream. The instructions associated with SISD are executed sequentially and the system may or may not have external; parallel processing capabilities.
Fig 3: SISD Architecture
Characteristics
- Standard von Neumann machine
- Instructions and data are stored in memory
- One operation at a time
Limitations
Von Neumann bottleneck
Maximum speed of the system is limited by the
Memory Bandwidth (bits/sec or bytes/sec)
- Limitation on Memory Bandwidth
- Memory is shared by CPU and I/O
Examples: Superscalar processors
Super pipelined