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What are the basic elements of a computer system overview according to William Stallings?
Processor, Main Memory, IO Modules, System Bus
What does the operating system do in a computer system?
Exploits the hardware resources of one or more processors, provides a set of services to system users, manages secondary memory and IO devices
What is the function of the Processor in a computer system?
Controls the operation of the computer, performs data processing functions, referred to as the Central Processing Unit (CPU)
What is the role of Main Memory in a computer system?
Stores programs and data, volatile, referred to as real memory or primary memory
What does IO Modules do in a computer system?
Handles input/output operations, interacts with external devices like printers, keyboards, monitors, etc.
What is the purpose of the System Bus in a computer system?
Provides communication between different components of the computer system, allows data transfer between processors, memory, and IO devices
What is the role of IO Modules?
Moves data between the computer and external environments such as storage, communications equipment, and terminals.
What is the function of System Bus?
Provides for communication among processors, main memory, and IO modules.
What are the main components of the computer system as shown in the diagram?
Processor, Main Memory, IO Modules, System Bus.
What are the registers shown in the diagram?
PC (Program Counter), IR (Instruction Register), MAR (Memory Address Register), MBR (Memory Buffer Register), IO AR (Input/output Address Register), IO BR (Input/output Buffer Register).
What is the purpose of the Execution unit in the CPU?
It reads and executes instructions fetched from memory.
What is the basic unit of a program?
A set of instructions stored in memory.
What does the Program Counter (PC) do in a processor?
Holds the address of the instruction to be fetched next and is incremented after each fetch.
What is the function of the Instruction Register (IR) in a processor?
The fetched instruction is loaded into the Instruction Register (IR) for interpretation by the processor.
What are the stages involved in the processor's instruction execution cycle?
Fetch Stage and Execute Stage.
Describe the steps involved in the instruction execution cycle: Step 1
PC 300, CPU Registers: 0 0 1 9 4 0, Memory: 301 5 9 4 1 302 2 9 4 1 940 0 0 0 3 941 0 0 0 2, AC IR: 1 9 4 0.
Describe the steps involved in the instruction execution cycle: Step 2
PC 300, CPU Registers: 3 0 1 0 0 0 5 0 0 0 5 0 0 0 3 0 0 0 5 1 9 4 0 301 5 9 4 1 302 2 9 4 1 940 0 0 0 3 941 0 0 0 2, AC IR: 5 9 4 1.
Describe the steps involved in the instruction execution cycle: Step 3
PC 300, CPU Registers: 3 0 2 1 9 4 0 301 5 9 4 1 302 2 9 4 1 1 940 0 0 0 3 941 0 0 0 2, AC IR: 5 9 4 1.
Describe the steps involved in the instruction execution cycle: Step 4
PC 300, CPU Registers: 3 0 1.
What are the contents of memory and registers in hexadecimal in Figure 14 of the example of program execution?
3 0 1 0 0 0 5 0 0 0 5 0 0 0 3 0 0 0 5 1 9 4 0 301 5 9 4 1 302 2 9 4 1 940 0 0 0 3 941 0 0 0 2 AC IR 5 9 4 1
What does Step 3 involve in the program execution process?
PC: 300, CPU Registers Memory: 3 0 2 1 9 4 0 301 5 9 4 1 302 2 9 4 1 1 940 0 0 0 3 941 0 0 0 2 AC IR 5 9 4 1
What interrupts the normal sequencing of the processor and why are they provided?
Interrupts interrupt the normal sequencing of the processor, provided to improve processor utilization as most IO devices are slower than the processor, and the processor must pause to wait for the device, avoiding wasteful use of the processor.
What are Interrupts?
Interrupts interrupt the normal sequencing of the processor.
Why are Interrupts provided?
Provided to improve processor utilization as most IO devices are slower than the processor, and the processor must pause to wait for the device, which is a wasteful use of the processor.
What are common classes of interrupts that can flow control without interrupts?
Short IO wait, long IO wait
What is the system utility that can take a long time without interrupts?
IO Program
What occurs during interrupts short IO wait in the flow of control?
User Program writes, IO Program writes, IO Program executes IO command, Interrupt handler ends with 1, 2a, 2b, 3a, 3b, 4, 5b
What occurs during interrupts long IO wait in the flow of control?
User Program writes, IO Program executes IO command, Interrupt handler ends with 1, 4, 5c
What is the state of the system during the instruction cycle with interrupts?
Interrupts can flow control and affect the flow of instructions
What is the Program Status Word (PSW) used for in interrupt processing?
A word of bits representing the current state of the interrupted program, including condition codes and kernel/user mode bit.
What are the hardware events that occur when an IO device completes an IO operation?
1. Interrupt occurs at location N 2. Program counter is saved 3. Transfer to the Interrupt Service Routine 4. Return from the interrupt to the user program
What is the purpose of the Interrupt Service Routine in interrupt processing?
To handle the interrupt, perform necessary operations, and return control to the user program.
How are interrupts handled when another interrupt is being processed simultaneously in a system?
Two approaches: 1. Disable interrupts while an interrupt is being processed 2. Use a priority scheme to determine the order of processing interrupts
What are some examples of multiple interrupts that can occur simultaneously?
Receiving data from a communications line and printing results at the same time, handling input/output operations from multiple devices like a printer and communications line
What are two approaches to disable interrupts while an interrupt is being processed?
Priority scheme and Transfer of Control With Multiple Interrupts
What is an example of Transfer of Control With Multiple Interrupts in action?
Printer interrupt or communications line interrupt
What are the basic elements of a computer system?
Processor, Main Memory, IO Modules, System Bus
What are the major constraints in memory trade-offs?
Amount, Speed, Cost
What is the principle of locality in memory hierarchy?
It states that a smaller, expensive fast memory is supplemented by a larger, cheap, slower memory
What is the purpose of the memory hierarchy in computer systems?
To optimize performance by utilizing different levels of memory with varying costs, capacities, and access times
Define Hit Ratio in the context of memory access.
Hit Ratio is the fraction of all memory accesses that are found in the faster memory level (L1 cache)
What is the trade-off involved in memory hierarchy design?
Trading off cost per bit, capacity, access time, and frequency of access to the memory by the processor
What happens if the byte to be accessed is in L1 cache?
The processor accesses it directly from L1 cache.
What happens if the byte to be accessed is in L2 cache?
The byte is transferred to L1 cache and then accessed by the processor.
What does 'Hit Ratio' refer to in cache memory?
Hit Ratio is the fraction of all memory accesses that are found in the faster memory, such as L1 cache.
What is the access time for L1 cache?
Access time for L1 cache is 1 microsecond (T1 = 1.01).
What is the access time for L2 cache?
Access time for L2 cache is 1 microsecond (T2 = 1).
What is the average access time for a byte in the Simple Two Level Memory system described in the text?
95 T1 + 5 T1 + 1 T2 + 0.15 s = 101.15 s
Why is supplementing with faster memory beneficial in the context of memory access time?
To exploit the principle of locality and to improve the average access time for memory operations.
What is the reason for the high value of 'H' in memory access performance?
The high value of 'H' is likely due to the Principle of Locality, where memory references by the processor tend to cluster.
What are the characteristics of temporal tendency in memory access described in the text?
The temporal tendency involves the processor accessing memory locations that have been used recently, such as accessing the same instructions repeatedly in a loop.
What is the motivation behind using Cache Memory in computer systems?
The motivation is to exploit the principle of locality and improve processor execution speed by utilizing a small, fast memory close to the processor.
What is the Temporal Tendency for processor to access memory locations that have been used recently?
In a loop, access the same instructions repeatedly.
What is Secondary Memory referred to as?
Auxiliary memory.
What are some characteristics of Secondary Memory?
External, nonvolatile, used to store program and data files, used to extend Main Memory.
What is the motivation for using Cache Memory?
To exploit the principle of locality and have a small fast memory cache between processor and main memory.
Why must the processor access memory at least once per instruction cycle?
Processor execution is limited by memory cycle time.
What is Cache Memory invisible to?
The operating system.
What are the principles similar to virtual memory that Cache Memory follows?
Principles similar to virtual memory Chapter 8.
What does the processor first check before accessing main memory?
Cache
Why is a block of memory copied into cache when not found?
Because of the locality of reference, it is likely that many future memory references will be to other bytes in the block
What is the structure of Cache and Main Memory like?
Cache and Main Memory Structure: 000 000 000 000 000 000 000 000 001 001 001 001 001 001 001 001 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 (eg. 6-bit Memory Addresses with K=8 tags, M=2^6=64 blocks)
What are the main categories of cache read operation?
Cache size, block size, mapping function, replacement algorithm, write policy, number of cache levels
What is Cache Size?
Small caches have a significant impact on performance.
What is Block Size?
The unit of data exchanged between cache and main memory.
What is Mapping Function?
Determines which cache location the block will occupy.
What is Replacement Algorithm?
Chooses which block to replace when a new block is to be loaded into the cache.
What is Least Recently Used (LRU) Algorithm?
An effective strategy to replace a block that has been in the cache the longest with no references to it.
What is Write Policy?
Dictates when the memory write operation takes place, can occur every time the block is updated or when the block is replaced.
What are the Basic Elements in a computer system?
Processor, Main Memory, IO Modules, System Bus.
What does direct memory access by IO hardware modules and multiple processors interfere with?
Direct memory access by IO hardware modules and multiple processors interfere with memory write operations.
What dictates when a memory write operation takes place?
The system bus dictates when a memory write operation takes place.
What are the basic elements of a system involving interference with direct memory access?
The basic elements are Processor, Main Memory, IO Modules, and System Bus.
Which elements are expanded in subsequent slides in the system involving direct memory access interference?
Each of the basic elements (Processor, Main Memory, IO Modules, and System Bus) are expanded in subsequent slides.
What are the three techniques possible for IO operations?
Programmed IO, Interrupt Driven IO, Direct Memory Access (DMA)
Describe how Programmed IO works.
Processor encounters IO instruction, issues instruction to appropriate IO module, repeatedly checks IO module status until instruction complete, transfers data between IO module and memory
Describe how Interrupt Driven IO works.
Processor issues an IO command to a module and continues with other work, IO module interrupts the processor when ready to exchange data, processor executes data transfer and resumes former processing
What are the drawbacks of Programmed and Interrupt Driven IO techniques?
Transfer rate limited by processor speed, processor tied up managing IO transfer, each transfer requires several instructions
What is Direct Memory Access (DMA) and how does it work?
Processor issues a command to DMA module for read or write data, DMA module handles data transfer between memory and IO module without processor intervention
What is former processing?
More efficient than Programmed IO, but still requires active intervention of the processor to transfer data between memory and an IO module.
What are the drawbacks of Programmed and Interrupt Driven IO?
Transfer rate is limited by the speed with which the processor can test and service a device, as data must traverse a path through the processor. The processor is tied up in managing an IO transfer, and each transfer requires several instructions.
What is Direct Memory Access (DMA)?
When the processor wishes to read or write data, it issues a command to the DMA module containing whether a read or write is requested, the address of the IO device involved, the starting location in memory to read/write, and the number of words to be read/written. DMA is performed by a separate module on the system bus or incorporated into an IO module.
What is a characteristic of direct memory access (DMA) transfers?
DMA transfers data directly to and from memory without involving the processor except at the beginning and end of the transfer.
How does the processor access the bus during a DMA transfer?
The processor accesses the bus slowly during a DMA transfer when it requires access for coordination purposes.
Why is DMA considered more efficient than interrupt-driven or programmed IO for multiple word IO transfers?
DMA is more efficient because it transfers multiple words directly between memory and IO modules without constant intervention from the processor.
What are the basic elements involved in a computer system with multiple processors (Symmetric Multiprocessors - SMP)?
The basic elements include processors, main memory, IO modules, and the system bus. All processors share access to IO devices.
How does SMP (Symmetric Multiprocessors) differ from a stand-alone computer system?
SMP systems have two or more similar processors that share the same main memory and are interconnected by a bus. They share access to IO devices and can perform parallel functions.
What are the advantages of using a system with multiple processors in SMP architecture?
The advantages include greater performance through parallel work, availability in case of a single processor failure, incremental growth by adding processors, and scalability with different products for various price and performance levels.
What is one benefit of parallel processing for processors?
Greater performance can be achieved.
How does the availability of multiple processors contribute to the overall system resilience?
The failure of a single processor does not halt the machine.
What is the concept of incremental growth in relation to adding processors?
An additional processor can be added to enhance performance.
Describe the advantage of scaling in terms of processor vendors.
Vendors can offer a range of products with different price and performance characteristics.
What does SMP stand for in the context of processor organization?
Symmetric Multiprocessing
What is a multicore computer also known as?
Chip multiprocessor
What is the main feature of a multicore computer?
Combining two or more processor cores on a single piece of silicon die
What components does each core of a multicore computer consist of?
All components of an independent processor
What type of cache is included in multicore chips in addition to the processor cores?
L2 cache and in some cases L3 cache
What are the basic elements of a multicore computer?
Instruction execution, interrupts, memory trade-off hierarchy
What is the main motivation behind using cache memory in computer systems?
To reduce the time taken to access data from the main memory by storing frequently accessed data closer to the processor
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Flashcard deck for computer system basics: elements, operating system functions, processor role, main memory function, IO module tasks.
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