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Revision (MAR (The memory address register holds any memory address about…
Revision
MAR
The memory address register holds any memory address about to be used by the CPU. The address might point to data or a CPU instruction
MDR
The memory data register holds the actual data or instruction. This may have been fetched from memory, or be waiting to be written to memory
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Purpose of the CPU
The purpose of the CPU is to process data. The CPU is where processes such as calculating, sorting and searching take place. Whatever is done on our computers, such as checking emails, playing games and doing homework, the CPU has processed the data we use.
ALU
The arithmetic and logic unit (ALU) is where the CPU performs the arithmetic and logic operations. Every task that your computer carries out is completed here. Even typing into a word processor involves adding binary digits to the file, and then calculating which pixels on the screen should change so that you can see the characters. The ALU’s operations fall into two parts:
-the arithmetic part, which deals with calculations, eg 1 + 2 = 3
-the logic part, which deals with any logical comparisons, eg 2>1
CU
The control unit controls and monitors communications between the hardware attached to the computer. It controls the input and output of data, checks that signals have been delivered successfully, and makes sure that data goes to the correct place at the correct time.
CACHE
A cache is a tiny block of memory built right onto the processor. The most commonly used instructions and data are stored in the cache so that they are close at hand. The bigger the cache is, the more quickly the commonly used instructions and data can be brought into the processor and used.
Fetch-Decode-Execute
The computer fetches the instruction from its memory and then executes it. This is done repeatedly from when the computer is booted up to when it is shut down.The first step the fetch-execute cycle carries out is fetching the instruction. The CPU fetches this from the main memory (the hard drive) and stores it in the CPU temporary memory, the immediate access store (the registers).Once the instruction has been fetched, the CPU will need to understand the instruction to action it. This is called decoding.When the instruction has been decoded, the CPU can carry out the action that is needed. This is called executing the instruction. The CPU is designed to understand a set of instructions - the instruction set.
Clock speed
Clock Speed. The clock speed (or clock rate) is stated in megahertz (MHz) or gigahertz (GHz), and refers to the speed at which the processor can execute instructions. The faster the clock, the more instructions the processor can complete per second.
Cache size
The cache is data storage inside the CPU that's much faster than RAM. A larger CPU cache gives the CPU faster access to more data it needs to process
Cores
A CPU can contain one or more processing units. Each unit is called a core. A core contains an ALU, control unit and registers. It is common for computers to have two (dual), four (quad) or even more cores. CPUs with multiple cores have more power to run multiple programs at the same time.
However, doubling the number of cores will not simply double a computer's speed. CPU cores have to communicate with each other through channels and this uses up some of the extra speed.
Embedded system
An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. Embedded systems control many devices in common use today.