1.1 - The characteristics of contemporary processors, input, output and storage devices
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What does the Arithmetic Logic Unit (ALU) do?
It is the problem solving part and performs arithmetic, logical + shift operations on data. The results are stored in registers.
What are the 4 arithmetic operations?
AND, OR, NOT, XOR. (Boolean Logic Operations)
What are shift operations?
Bits are moved left or right in a register.
What is the Central Processing Unit (CPU)?
It is the brain of the computer, it does all the calculations & processes instructions.
What are registers?
Several locations of superfast memory to temporarily store results. Small memory cells that operate at a very high speed. They are used to temporarily store data and all arithmetic, logical and shift operations occur in these registers.
What are the 5 special purpose registers?
• Program Counter (PC). • Current Instruction Register (CIR). • Memory Address Register (MAR). • Memory Data Register (MDR). • Accumulator (ACC)
What does the PC do?
It holds the memory address of the next instruction to be executed.
What does the CIR do?
It holds the current instruction and splits it into Opcode + Operand.
What does the MAR do?
It holds the address in memory where the processor is required to fetch/store date to/from.
What does the MDR do?
It temporarily holds data moving between the processor and main memory.
What does the ACC do?
It holds intermediate results of an instruction.
What 3 things need to be held in order for a instruction to be executed?
• Current instructions must be temporarily held by the processor before being executed. • The address of the data + the actual data must be held. • The address of the next instruction being executed must also be held.
What happens if a computer has more cores?
It is faster.
What are the 5 things the Contol Unit (CU) does?
• It controls & coordinates all the activities of the CPU. • Managing the flow of data between the CPU and other devices. • Accepting the next instruction. • Decoding instructions. • Storing the resulting data back in memory.
What are Buses?
A series of connectors that transfer signals between internal components. Transferring of data.
What is the System Bus?
It is 3 seperate buses carrying control signals, addresses + data.
How are control signals transported?
Control signals are sent along the control bus between the CU and other components.
What is memory read?
Data from the addressed location in RAM is placed on the data bus.
What is memory write?
Data on the data bus is written to the addressed locations in RAM.
What is bus request?
It Indicates a device is requesting to use the data bus
What does the clock do?
It synchronises operations
What are the 2 features of the data bus?
• This is a bi-directional bus (meaning bits can be carried in both directions). - This is used for transporting data and instructions between components.
What are 2 features of the address bus?
• Transmits the memory addresses specifying where data is to be sent to or retrieved from. • The width of the address bus is proportional to the number of addressable memory locations. e.g 8 bit address bus -> maximum number of memory addresses = 2(∧8) = 256
What are 2 features of the control bus?
• bi-directional bus used to transmit control signals between internal and external components. • The control bus coordinates the use of the address and data buses and provides status information between system components.