1.1 The characteristics of contemporary processors, input, output and storage devices Flashcards
What is a processor?
seen as ‘the brain’ of the computer
-executes instructions allowing programs to run
What is the function of the ALU
arithmetic and logic unit- completes the arithmetical and logical operations
What is the function of the control unit? Give examples (3)
directs operations inside the CPU
-controls and coordinates activities of the CPU
-manages flow of data between CPU and other devices
-decodes instructions
What are registers? What do they do?
-small memory cells which operate at very high speeds
-used to temporarily store data such as arithmetic, logical and shift operations
Name all the registers (5)
-program counter (PC)
-accumulator (ACC)
-memory address register (MDR)
-memory data register (MAR)
-current instruction register (CIR)
What is the PC used for?
program counter (PC) - holds address of the next instruction to be executed
What is the ACC used for?
accumulator (ACC) - stores results from calculations
What is the MAR used for?
memory address register (MAR) - holds address of a memory location that has been fetched or data that needs to be written
What is the MDR used for?
memory data register (MDR)- temporarily stores data that has been read or data that needs to be written
What is the CIR used for?
current instruction register (CIR) - holds current instruction being executed, divides it into operand and opcode
What is the data bus used for?
-a bi-directional bus (data/bits can be carried in both directions)
transports data and instructions between components
What is the address bus used for?
transmits the memory addresses specifying where data is to be sent to or retrieved from
What is the control bus used for?
-a bi-directional bus (data/bits can be carried in both directions)
transmits control signals between internal and external components
What type of signals are given out by control buses? (6)
-bus request: shows that a device is requesting the use of the data bus
-bus grant: shows that the CPU has granted access to the data bus
-memory write: data is written into the addressed location using this bus
-memory read: data is read from a specific location to be placed onto the data bus,
-interrupt request: shows that a device is requesting access to the CPU
-clock: used to synchronise operations
In the decode phase of the FDE cycle, what is the instruction divided into? Where?
opcode and operand
-in the CIR
What do we mean by opcode?
a section of the instruction used to determine what type of instruction it is and what hardware is needed to execute it
What do we mean by operand?
a section of the instruction which tells us the address of where the operation is performed
What is the FDE cycle?
fetch-decode-execute cycle is the sequence of operations that are completed by the cpu to execute an instruction
What happens during the fetch phase of the FDE cycle? (4)
-address from PC is copied to the MAR
-instruction held at that address is copied to MDR via data bus
-simultaneously, the contents of the PC increment by 1
-value held in MDR is copied to the CIR
What happens during the decode phase of the FDE cycle? (1)
the contents of the CIR are split into operand and opcode
What happens during the execute phase of the FDE cycle? (1)
the opcode is executed on the operand
What is pipelining?
the process of completing the different stages of the FDE cycle simultaneously
What are some limitations of pipelining? (2)
-programs with lots of branched instructions may not benefit from the effects of pipelining
-some instructions may need to be flushed if the instruction branches off
What are the different types of computer architecture? (3)
-von neumann
-harvard architecture
-contemporary processing
What characteristics does Von Neumann architecture have?
-shared memory and data bus used for both data and instructions
-includes a single control unit, registers and memory units
What are some advantages of Von Neumann architecture? (2)
-cheaper to develop since the control unit is easier to design
-programs can be optimised to design
What characteristics does harvard architecture have?
-physically separate memory for instructions and data
What are some advantages of harvard architecture? (2)
-faster to use as pipelining is possible
-both memories can be different sizes
What are some characteristics of contemporary processing/architecture? (3)
-combination of both harvard and von neumann architecture
-uses von neumann when working with the data and instructions in main memory
-uses harvard when working with cache
What are some factors affecting CPU performance? (3)
-clock speed
-number of cores
-cache
What is clock speed and how does it affect the CPU performance?
-the number of clock cycles completed in a second (measured in Ghz)
-faster clock speed, faster performance
What do we mean by a core and how does it affect CPU performance? What are some limitations with this?
-an independent processor able to execute its own FDE cycle
-more cores, more FDE cycles able to be completed
-some programs aren’t optimised for use of more than one core
What is cache and how does it affect CPU performance?
-small memory location located on or near the CPU, holds frequently used data
-quicker to access instructions from cache instead of main memory
-as it fills up, unused instructions get replaced
What are the different types of cache and what are their properties?
Level 1- very fast, small capacity
Level 2- relatively fast, medium sized capacity
Level 3- slower, much larger capacity
What are the two types of instruction sets?
RISC (reduced instruction set computers)
CISC (complex instruction set computers)
What are some characteristics of a RISC processor? (4)
-small instruction set
-each instruction= 1 line of machine code
-used in common computers
-pipelining is possible= 1 instruction takes 1 clock cycle
What are some characteristics of CISC processors? (4)
-large instruction set
-instructions are built into hardware
-used in microcontrollers and embedded systems
-many specialised instructions
What are some +/- of CISC? (2 +/- each)
+ CISC
-compiler has to do less work
-less RAM required to store the code
-CISC
-increased energy consumption
-may take more than 1 clock cycle to complete
What are some +/- RISC? (2 +/- each)
+ RISC
-lower energy requirement
-can support pipelining
-RISC
-heavy use of RAM (can cause bottlenecks-processing capability is limited due to the RAM being insufficient)
-compiler has to do more work
What is a GPU?
graphics processing unit
-a co-processor (an additional processor used for specific tasks) made up of lots of independent processor
What are the features of a GPU? (3)
-efficient at carrying out simple tasks on larger data sets
-can carry out SIMD (single instructions on multiple data)
-can work in parallel
What is a GPU mainly used for? (5)
initially used for graphics processing
-weather modelling
-password cracking
-machine learning
-data mining
-doing complex calculations
Compare a GPU to a CPU (2)
-GPUs are efficient at carrying out simple tasks on larger data sets whereas CPUs are efficient at carrying out complex calculations on small data sets
-GPUs can carry out one instruction on multiple pieces of data while CPUs cannot
What are multicore processors?
CPUs which have multiple independent cores, each completing its own FDE cycle (can carry out pipelining efficiently)
What do parallel systems do?
accomplish tasks (also through pipelining) using a single core and threading (the capacity of a program to utilize different processors)
What are some examples of input devices? (5)
-keyboards
-webcams
-mouse
-scanners
-microphone
What are some examples of output devices? (3)
-speakers
-printers
-projectors
What are the three types of storage? Give examples (3 each)
Optical
-CD
-DVD
-Blu-ray
Magnetic
-hard disk drives
-magnetic tapes
-floppy disk
Solid state
-solid state drive
-flash memory card
-USB stick
What are some +/- of optical storage? (2+, 3-)
+ cheap
+portable
-slow access times
-fragile
-limited/low capacity
What are some +/- of Magnetic storage? (3 each)
+large capacity
+low cost per GB
+suitable for long term storage & backup
-not durable (has moving parts)
-slow read/write times
-not portable
What are some +/- of solid state storage? (3+, 2-)
+durable
+fast read/write times
+portable
-high cost per GB
-sometimes has limited capacity
-can wear out after a certain number of write cycles
What are the factors to consider for storage? (5)
-capacity
-speed
-cost
-durability
-portability
What are the two types of primary storage?
-RAM (random access memory)
-ROM (read-only memory)
What does volatile mean?
if something is volatile, when its power is lost, its information is also lost
What is RAM? (3)
-fast, volatile memory
-can be written to and read from
-used to store temporarily store data and programs that the computer/CPU is currently using
What is ROM? (3)
-non-volatile memory
-can only be read from
-stores the computer’s start-up routine (bootstrap/BIOS)
What is virtual storage?
storing information remotely e.g cloud storage
What are some +/- of virtual storage? (4+, 5-)
+data can be accessed anytime from any device as long as there is internet access
+data can be easily shared without the need for removable media transfer
+easy to collaborate
+can back up data
-can be expensive
-if connectivity is poor, access times can be slow
-if there isn’t an internet connection, you can lose access to files
-if data is stored in a different country, other laws apply
-privacy concerns (relying on a third party)
How does INP make use of registers?
when INP is used, the ACC stores a value
How does OUT make use of registers?
when OUT is used, the value is currently in the ACC
How does LDA make use of registers?
data from RAM goes to MDR (with help of MAR)
How does STA make use of registers?
value from ACC goes to MDR then sent to RAM (with help of MAR)
How do BRA/BRZ/BRP make use of registers?
comparison takes place in ALU
How does ADD/SUB make use of registers?
carried out in ALU, result stored in ACC
