Operating Systems: Computer System Overview Chapter 1 Quiz

Interrupt Handling

• Two approaches to handle interrupts: disabling interrupts while processing an interrupt, and using a priority scheme
• Transfer of control with multiple interrupts involves handling interrupts in a specific order

Memory Hierarchy

• Major constraints in memory: amount, speed, and expense
• Memory must keep up with the processor and be reasonably priced
• Greater capacity = smaller cost per bit, faster access time = greater cost per bit, and greater capacity = slower access speed
• Memory references by the processor tend to cluster, and data is organized to minimize access to lower levels of memory

Memory Relationships

• Going down the hierarchy: decreasing cost per bit, increasing capacity, increasing access time, and decreasing frequency of access
• Principal of locality: use a small, fast memory to store frequently accessed data

Cache and Main Memory

• Cache contains a copy of a portion of main memory
• Processor first checks cache, and if not found, a block of memory is read into cache
• Cache/Main-Memory Structure: cache size, number of cache levels, and block size

Cache Design

• Cache size: small caches have a significant impact on performance
• Block size: the unit of data exchanged between cache and main memory
• Mapping function: determines which cache location a block will occupy
• Replacement algorithm: chooses which block to replace when a new block is loaded into the cache
• Write policy: dictates when the memory write operation takes place

Symmetric Multiprocessors (SMP)

• A standalone computer system with multiple similar processors
• Processors share the same main memory and I/O devices
• Processors can perform the same functions and are controlled by an integrated operating system

Performance Scaling

• Adding multiple processors can yield greater performance if work can be done in parallel
• Vendors can offer a range of products with different price and performance characteristics

Multicore Computer

• Combines two or more processors (cores) on a single piece of silicon
• Each core consists of an independent processor and includes L2 cache and in some cases L3 cache

Operating System

• Manages hardware resources of one or more processors
• Provides a set of services to system users
• Manages secondary memory and I/O devices

Basic Elements

• Processor: controls the operation of the computer and performs data processing functions
• Main Memory: volatile, contents lost when the computer is shut down
• I/O Modules: moves data between the computer and external environments
• System Bus: provides communication among processors, main memory, and I/O modules

Instruction Execution

• A program consists of a set of instructions stored in memory
• Two steps: processor reads (fetches) instructions from memory, and processor executes each instruction

Basic Instruction Cycle

• Processor fetches the instruction from memory
• Program counter (PC) holds the address of the instruction to be fetched next
• Instruction Register (IR) holds the fetched instruction