1.1 Systems Architecture

flashcards for the whole of 1.1 following the specification

purpose of the cpu

to perform the fetch decode execute cycle

what happens at the fetch section of the fde cycle?

causes the next instruction and any data

involved to be fetched from main memory

what happens at the decode section of the fde cycle?

decodes the instruction

what happens at the execute section of the fde cycle?

executes the instruction

explain the F-E cycle step by step

• PC → MAR: The Program Counter (PC) sends the address of the next instruction to the Memory Address Register (MAR).

• Fetch Instruction: The instruction at the MAR's address is fetched and placed into the Memory Data Register (MDR).

• Decode: The Control Unit decodes the instruction and decides if more data is needed.

• Fetch Data: If needed, the MAR holds the address of the required data in memory.

• Data Fetch: The data is fetched from memory and placed in the MDR for processing.

Von-Neumann architecture

consists of ALU, CU, memory units (eg RAM) and inputs and outputs

both instruction data and program data are stored in the same memory in binary

contains four registers - MDR, MAR, PC and accumulator

ALU

Arithmetic Logic Unit

where the arithmetic operations are done

CU

Control Unit

coordinates and controls all of the activities taking place within the CPU (e.g decoding and executing instructions)

cache

located on the CPU

it is slower to access than registers but faster than RAM

stores frequently accessed data

registers

a very fast memory location in the CPU itself

MAR

Memory Address Register

holds the memory address of the current instruction, and then the data that it uses, so that these can be fetched from memory

MDR

Memory Data Register

holds the actual instruction, and then the data that has been fetched from memory

PC (VNA)

Program Counter

holds the address of the next instruction to be executed

Accumulator

holds the result of an instruction (aka results of arithmetic and logic calculations) before it is transferred to memory

what is the difference between storing data and an address

addresses are stored in the Memory Address Register and data is stored in the Memory Data Register

how does clock speed affect cpu performance?

the faster, the clock speed, the faster instructions are processed = better cpu performance

how does cache size affect cpu performance

larger cache size improves CPU performance by storing more frequently used data, reducing the time needed to access slower main memory.

how does the number of cores affect cpu performance?

more cores allows the computer to complete more tasks at the same time improving cpu performance (quad is better than single core processor)

clock speed

Cycles per second, measured in hertz (Hz)

1Hz = 1 instruction/one cycle carried out a second

number of cores

The number of duplicate processing units (cores) placed in one CPU

embedded system

a single microprocessor that includes RAM, ROM and a CPU

purpose of embedded system

to control the device and to allow a user to interact with it

give 3 examples of embedded systems

• dishwashers

• smart phones

• microwave ovens

• digital cameras

• smart thermostats

characteristics of embedded systems

• typically slow cpu speed

• software has one purpose

• cannot install new software

• programs stored on the ROM

• typically very reliable (only programmed to do one thing)