Processors, I/O and storages devices Flashcards by Dawid Milosierny (Student)

Describe the fetch stage of the FDE cycle

-Contents of PC copied from PC to MAR
-Address is sent along address bus
-Control unit sends a read signal to main memory along control bus
-Content stored in memory address copied to MDR (sent along data bus)
-PC incremented to next instruction
-Contents of MDR copied to CIR

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Describe the decode stage of the FDE cycle

-Instruction held in CIR is decoded by the CU, split into opcode and operand
-Opcode determines type of instruction and hardware needs
-Operand holds either the address of the data (copied to MAR), the actual data (copied to MDR) or the data to be operated on (copied to ALU/ACC)

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Describe the execute stage of the FDE cycle

Instruction carried out on the operand

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What is the function of the control unit?

-Synchronisation of FDE cycle
-Sends control signals to coordinate movement of data through processor
-Controls buses

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What are registers and why are the needed?

-Temporary storage/memory location inside the CPU, used for a specific purpose
-Needed because they allow fast access to frequently needed data (1), faster that accessing RAM/secondary storage (1)

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In what situation may a register value change?

-PC increments during FDE cycle
-Jump instruction from CIR (1), PC changes to address given (1)

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What is the function of the program counter?

PC stores address of next instruction, sends this to MAR then increments

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What is the function of the memory address register?

MAR stores the memory location of the data to be fetched

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What is the function of the memory data register?

MDR stores the data from memory location specified by MAR

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What is the function of the address bus?

Address bus transfers the memory location to access the data

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What is the function of the data bus?

Data bus transfers the data from the memory location specified by MAR

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What is the function of the control bus?

Control bus transmits control signals from the control unit

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What is the function of the accumulator?

-Holds all input/output
-Holds results of calculations (from the ALU)
-Checked for conditional branching (e.g. BRZ)
-Stores data which has come from the MDR/RAM
-Temporary storage for data being processed / during calculations
-I/O in processor, used as buffer

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What is a GPU?

-Specialised electronic circuit for graphics
-Has parallel structure
-Thousands of small but efficient cores
-Can process huge blocks of visual data simultaneously
-However, CPU is general purpose
-SIMD device (Single Instruction, multiple data)

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What is meant by CISC?

-Complex instruction set computer
-Each instruction may take multiple cycles
-Single register set
-Many instructions available
-Complicated processor design
-Integrated circuit is expensive

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What is meant by RISC?

-Reduced instruction set computer
-Each instruction performs a single task
-Limited number of instructions available
-Complex tasks can only be performed by combining multiple instructions
-Simple processor design (less transistors)

Explain one advantage of RISC over CISC

Programs run faster (1) due to simpler instructions (1)

What is meant by a coprocessor?

-Does floating point arithmetic
-Can do calculations
-So processing is faster

What are the characteristics of Von Neumann architecture?

-Instructions executed in linear sequence
-Single control unit
-One instruction at a time
-FDE cycle
-Instructions and data stored together / in the same format

What is meant by array processing?

-Single instruction multiple data (SIMD)
-Allows same instruction to operate simultaneously on multiple locations / many ALU’s

What is pipelining and how does it improve performance?

-Concurrent processing of multiple instructions
-One instruction can be fetched whilst the previous one is being decoded…
-…and the one before is being executed.
-In case of a branch pipeline is flushed
-Increases throughput
-Prevents idle components

What are the characteristics of Harvard architecture?

-Uses separate memory blocks for instructions and data
-Has separate buses (data and address) for data and instructions
-Has fixed memory sizes for data and instructions
-Instruction memory may be ROM
-Can read/write data and instructions
simultaneously (2024 MS)

What is meant by a character set?

-Number of values represented with n bits is 2^n
-Character set means all the characters a computer can understand (1), may include control characters (1), binary code equates to symbols (1), e.g. ASCII (1)

What is Unicode?

-Each character is represented by 1-4 bytes
-Supports very large number of characters
-Backward compatible with ASCII

What is a D-type flip flop?

Stores a value of one bit when signal is given

How does a magnetic hard drive work?

Works by magnetic patterns being read off platters that mechanically spin at high speeds

Explain a disadvantage of a magnetic hard drive

-Not very portable, as it is susceptible to damage if moved quickly/suddenly due to head coming in contact with platter

How does a solid state drive work?

They use memory chips, which can have contents erased and subsequently overwritten when electrical charge is applied

Explain an advantage of a solid state drive

-No moving parts, so can be compact -Silent, so lower power consumption

How does optical media work?

-Read / written to, using a laser -Read / written onto a reflective surface -Data is stored using pits and lands -E.g. Blu-Ray / CD

State the advantages of optical media

– Cheap to produce / buy – Capacity big enough to hold film – Robust enough to be used over long periods / moved around – Portable – Does not need an internet connection

What is meant by RAM?

-Random Access Memory -A form of primary memory -Used to hold data and / or programs in use (active/running data) -Volatile / Loses its contents when power is lost

What needs to be stored in RAM?

-Software / user files need to be stored in RAM to offer direct access and allow use to alter contents of files, fast read/write speeds

How does adding RAM improve performance?

-Reduces reliance on VM, and RAM is faster to access than VM, and it prevents disk thrashing

What is meant by ROM?

-Read only memory -Volatile -Stores boot program (bootstrap loader) -Quick to start up

What are some uses of ROM in embedded systems?

-Storing OS as it doesn’t need to be updated, so it is quicker to access -Storing encryption keys that cannot be changed -Used as primary/secondary storage

What is BIOS and what does it do?

-Basic input/output system -Contains the computer start-up instructions -Loads settings/configuration (CMOS) -Checks hardware devices are available / carries out POST (power-on self-test) check -…and reports errors -Determines the drive on which OS is stored -Loads the bootstrap / OS (into main memory)

What is meant by virtual storage, state its advantages?

-Virtual storage is storage that appears to the user as local, but is actually stored on remote servers and accessed via the internet, such as in cloud storage solutions (CHAT GPT) -Can be accessed from elsewhere / other machines -Storage can be expanded as necessary//no limit on size -No on site maintenance required -Allows more local storage capacity for data