Computer Science AS OCR
-
1-1-structure-and-function-of-the-processor as5 主题
-
1-2-types-of-processor as3 主题
-
1-3-input-output-and-storage as2 主题
-
2-1-systems-software as8 主题
-
2-3-software-development as5 主题
-
2-4-types-of-programming-language as4 主题
-
3-1-compression-encryption-and-hashing as3 主题
-
3-2-databases as3 主题
-
3-3-networks as8 主题
-
3-4-web-technologies as13 主题
-
html as
-
css as
-
css-styling as
-
javascript as
-
variables-and-constants-in-javascript as
-
outputs-in-javascript as
-
selection-in-javascript- as
-
for-loops-in-javascript- as
-
while-loops-in-javascript- as
-
strings-in-javascript- as
-
operators-in-javascript- as
-
nested-statements-in-javascript as
-
functions-and-procedures-in-javascript as
-
html as
-
4-1-data-types as8 主题
-
4-2-data-structures as4 主题
-
4-3-boolean-algebra as1 主题
-
5-1-computing-related-legislation as4 主题
-
5-2-moral-and-ethical-issues as9 主题
-
6-1-thinking-abstractly as3 主题
-
6-2-thinking-ahead as1 主题
-
6-3-thinking-procedurally as3 主题
-
6-4-thinking-logically as2 主题
-
6-5-thinking-concurrently as2 主题
-
7-1-programming-techniques as9 主题
-
8-1-standard-algorithms-and-big-o-notation as8 主题
components-of-the-cpu as
Exam code:H046
Components of the CPU
What is the CPU?
-
The CPU is responsible for processing all data within the computer
-
It is made up of a number of components including:
-
Arithmetic and Logic Unit (ALU)
-
Control Unit (CU)
-
Registers
-
-
Registers are temporary storage/memory locations inside the CPU which are used for a single specific purpose
-
They have a faster access speed than RAM / secondary storage
-
There are a number of registers in the CPU:
-
Program Counter (PC)
-
Accumulator (ACC)
-
Memory Address Register (MAR)
-
Memory Data Register (MDR)
-
Current Instruction Register (CIR)
-
|
Component |
Function |
|---|---|
|
Arithmetic and Logic Unit (ALU) |
This performs any arithmetic calculations (e.g. adding binary) or any logic comparisons (using AND, OR, NOT) The ALU is made up of several components |
|
Control Unit |
This is where instructions are decoded. The CU also controls the data within the CPU and how it moves around |
|
Program Counter (PC) |
This stores the address in memory of the next instruction to be fetched |
|
Accumulator (ACC) |
This is where values are stored temporarily, either after they’ve been inputted or loaded, or after being calculated in the ALU |
|
Memory Address Register (MAR) |
This is where addresses are stored, either for where data is being sent in memory, or where it is being fetched from |
|
Memory Data Register (MDR) |
This is where data/instructions are stored, either before it sent to memory, or after being fetched |
|
Current Instruction Register (CIR) |
When an instruction has been fetched from memory it is loaded here before being split into opcode and operand. After this, it will be decoded. |
-
The ALU is made up of several components:
-
Arithmetic circuit
-
This carries out any arithmetic (addition, subtraction, multiplication or division)
-
-
Logic circuit
-
This carries out operations like AND, OR, NOT, XOR
-
-
Registers
-
These are additional registers to those mentioned above and can store data
-
-
Status flags
-
This includes overflow flags (if the value is too large for the register) or could include a zero flag (to tell if the answer is 0 easily)
-
-
Buses
-
These are used to transport data around the ALU and to other parts of the CPU
-
-
Buses
-
There are 3 buses which connect the CPU with the main memory (RAM):
-
Data bus
-
Address bus
-
Control bus
-
|
Bus |
Purpose |
Operation |
|---|---|---|
|
Data Bus |
Holds data being sent to/from the CPU and RAM |
Read/Write |
|
Address Bus |
Holds addresses being sent to/from the CPU and RAM |
Read/Write |
|
Control Bus |
Sends Signals to determine whether the other buses are in read or write mode |
Sends signals |
-
There are also a number of other buses within the CPU which transport data between the different areas
Responses