Flashcards in U2T3 (1) - Hardware + Software Deck (176)
What is a computer system?
A system that is able to take a set of inputs, process them + create a set of outputs which is done by a combination of hardware + software.
What do you need for processing to take place? What is this system called?
A program which is a set of instructions. A stored-program computer.
What are the internal components of a computer system?
Motherboard, CPU, hard drive, RAM memory, graphics card, optical drive, power supply + heat sink/fan.
What is inside the CPU? Other names?
Control unit (CU), memory (cache) + arithmetic + logic unit (ALU) - Processor/central processing unit.
What does the CU do?
Control operation of CPU + hardware components by following program, organises storage + transfer of data using internal memory + special registers, performs fetch-decode-execute cycle by using register to step through instructions in sequence.
What do these mean?:
Fetch, decode, execute.
An instruction is copied from memory to CPU.
Meaning of instruction is determined.
Appropriate action is taken/calculation performed.
What does the ALU do?
Calculations (+/-/x/divide), comparisons (>/=), logical functions (and/or/not), bit-shift operations (shift bits in word right/left) Contains decoder + registers too.
What is the decoder?
Logic circuit to take binary rep of instruction + initiate execution of instruction. Part of ALU.
What are the registers?
Small pieces of memory inside CPU. Hardware version of variable in software.
What are the 3 steps that computers go through?
Input, process, output.
What are the 3 types of memory in the IAS? What is the IAS?
Immediate access store.
RAM, ROM + cache.
What is RAM? Typical size in computer?
Temporarily stores programs/data currently being executed. Content can be changed as it is temp. When programs are loaded from hard drive they are put into RAM. Allows programs to be quicker. 512 MB. Volatile. Read to/written from.
What is ROM?
Perm stores booting up part of operating system program. Non-volatile. Read from, not written to.
What is cache memory?
Fast access RAM close to CPU. Stores recent + frequent files. Volatile. Used by proxy server.
What are the registers in the CPU? (6)
IR, MDR, MAR, PC, ACC, general purpose.
What is the IR and what does it do?
Instruction register holds instruction currently being executed.
What is the MDR and what does it do?
Memory Data Register/memory buffer register/data buffer holds data that has been fetched from memory.
What is the MAR and what does it do?
Memory Address Register holds address of next piece of memory to be fetched.
What is the PC and what does it do?
Program Counter holds address of next instruction to be fetched from memory. Automatically incremented between supplying address of next instruction + instruction being executed.
What is the ACC and what does it do?
Accumulator is an internal CPU register used as default location to store calculations performed by ALU.
What are the general purpose registers used for?
Store transient data required by program. e.g. when a program is interrupted, its state may be saved here, ready for recall when it's ready to start again.
What is the state of a program?
Value of registers e.g. PC/IR/MAR
If a CPU has ___ registers available, it will work faster.
What is the fetch-decode-execute cycle?
The sequence that is completed for each instruction in a program.
Describe each step of the fetch-decode-execute cycle?
Data + program that acts upon it are loaded into main memory (RAM) by operating system. PC copies address of next instruction into MAR, MAR places address onto Address bus, MAR triggers read signal causing RAM to place instruction onto data bus, this is loaded into MDR which copies it into IR. Decoded from instruction set in CPU and areas are prepared for execution. Instruction is now executed and CPU sets up for next cycle.
What are the 4 key factors of about CPU architecture that affect its performance?
Cores, clock speed, cache size + processor type.
What processing units does the CPU contain? What does eat unit contain? How many units might it have and why?
Cores. ALU, control unit & registers. 2 (dual), 4 (Quad) or even more. Runs multiple programs at the same time.
If I double the number of cores from 2 to 4, how much does my speed increase?
It won't double as some is used up in communicating with each other through channels.
What is the clock speed?
Clock rate, indicates how fast the CPU can run. Measured in MHz or gHz and corresponds with how many instruction cycles the CPU can deal with in a second.