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Florida State College at Jacksonville *

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4640

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Electrical Engineering

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Oct 30, 2023

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docx

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Parallel processing (multiprocessing) - 2 or more CPUs execute instructions simultaneously - Processor Manager o Coordinates activity of each CPU o Synchronizes interaction among CPU - Development o Enhances throughput o Increases computing power - Benefits o Increased reliability (since there are 2 CPUs instead of 1) o Faster processing performance - Faster instruction processing methods o CPU allocated to each program/job o CPU allocated to each working set or parts of it o Individual instructions subdivided  Each subdivision processed simultaneously => Concurrent programming - 2 challenges o Connecting processors into configurations o Orchestrating processor interaction - Synchronization is key to the system’s success in a parallel processing environment Evolution of multiprocessors - Developed for high-end midrange and mainframe computers o Each additional CPU treated as additional resource - Multi-core processing - Several processors placed on a single chip - Problem: heat and current leakage - Solution: o Single chip with 2 processor cores in same space  Allows 2 sets of simultaneous calculations  80 or more cores on single chip o 2 cores each run more slowly than single core chip

Master/Slave configuration - - All depends on master processor, risk of bottleneck Loosely Coupled Configuration - Tightly Coupled Configuration - Process Synchronization Software - Successful process synchronization in an OS requires the OS to: o Lock up a resource in use by process  Protect resource from other processes until released o Only when resource is released  Waiting process is allowed to use resource

- Mistakes in synchronization can lead to o Starvation o Deadlock - Critical region o Part of a program o A process must be allowed to finish work on a critical part of the program before other progresses can have access to it. It is called a critical region because it is a critical section and its execution must be handled as a unit  Other processes must wait before accessing critical region resources - Process within critical region o Cannot be interleaved since it threatens integrity of operation - Synchronization o Implemented as lock-and-key arrangement  1. Process determines key availability  2. If key is available, process picks up key, put key in lock making it unavailable to other processes o Type of locking mechanisms  Test and set  Executed in single machine cycle to see if key is available, and if it is, set key to unavailable  Actual key is a single bit in storage location: zero (free) or one (busy)  WAIT and SIGNAL  WAIT: activated when process encounter busy condition code  SIGNAL: activated when process exits critical region and condition code set to “free”  Semaphores  Nonnegative integer variable sets as a flag. Signals if and when resource is free  2 operations (let s be a semaphore variable): o P (probegen means “to test”): if P(s), if s>0, then s = s-1 o V (verhogen means “to increment”): if V(s), s = s+ 1 o S = 0 implies busy critical region (process calling on P operation must wait until s > 0)

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  Process Cooperation - Producers (produces data) and Consumers (consumes data) - Threads and Concurrent Program - Threads: small unit within process - Minimizes overhead of swapping process between main memory and secondary storage - Each active process thread: Processor registers, program counter, stack and status - Shares data area and resources allocated to its process

- Thread Control Block (TCB) -