Single vs Multiprocessor Systems

Study Notes

Comprise one main CPU capable of executing a general-purpose instruction set, including user process instructions.
May include special purpose processors for specific tasks, like I/O processors in mainframes, which have a limited instruction set and do not run user processes.
Managed by the operating system, which sends task information and monitors execution status of special purpose processors.
Example: A disk controller microprocessor handles requests from the main CPU and implements its own scheduling algorithm, alleviating the CPU from disk scheduling responsibilities.
Example: PCs utilize a keyboard microprocessor to convert keystrokes into codes sent to the CPU.
Special purpose processors do not alter a single processor system into a multiprocessor system.

Feature more than one processor that operates in close communication, also known as tightly coupled or parallel systems.
Share critical resources such as the computer bus, clock, memory, and peripheral devices.
Capability for multiple processes to run simultaneously in parallel.
Advantages include:
- Increased Throughput: More processors lead to higher work output in less time, though the speed-up ratio is less than linear based on the number of processors.
- Economy of Scale: Shared peripherals, mass storage, and power supplies lead to cost savings compared to running multiple single processor systems; data can be centralized on one disk for accessibility by all processors.
- Increased Reliability: Properly distributed programs across processors ensure that the system continues functioning even if one processor fails, merely resulting in reduced performance rather than a complete halt.