1.1 Systems Architecture

Cache

• Storage which is Bigger than Registers and smaller than RAM
  -Located on the CPU so data does not have to travel too far to get to RAM
  -provides quick access to frequently used instructions

Registers

Small , very fast pieces of memory built inside the CPU that immediately handles temporary data/instructions

MAR (Memory Address Register)

Holds the address of where data is to be fetched or stored

MDR (Memory Data Register)

Holds the data fetched from, or to be written to the memory

Program Counter

holds the address of the next instruction to be executed

Accumulator

Stores results of calculations in the ALU

Fetch stage

CPU Fetches instruction from main memory -RAM

Decode stage

Instruction is broken down by CU in CPU, so computer can understand

Execute stage

The instruction is then performed and carried out

ALU (Arithmetic Logic Unit)

performs arithmetic calculations and logical operations

CU(Control Unit)

controls the flow of data in the CPU and decodes instructions in the FDE cycle

The difference between storing data and an address

data is the actual value/info to be processed
Address is a location in memory where data is stored

What are Three factors that affect the CPU performance?

-Clock speed
-Cache size
-Number of cores

Effect of clock speed

-Num of instructions a single processor core can carry out per second (Hz)
-The faster the clock speed, the faster the computer can perform the FDE cycle , so the more instructions processed each second

GHz

billions of cycles per second

Effect of number of cores

-A core is a single processing unit in CPU
which is each able of FDE its own instructions
-The more cores there are, the greater number of instructions it can process simultaneously , in a given space of time

Effect of cache size

-Cache is a small amount of high-speed RAM built on the processor
-The bigger the cache , the less time a processor has to wait for instructions to be fetched
-Cache has faster read/write speed than RAM

Dual-core vs quad-core

-dual core has 2 processing units
- quad core has 4 processing units

Embedded systems

A computer system, with a single function , built into a larger machine

Characteristics of embedded systems

-easier to design
-cheaper to produce
-less power needed
-smaller in size