Unit 1 - Components of a computer Flashcards
What are the CPU components
CU(Control Unit)
Buses
ALU(Arithmetic Logic Unit)
Dedicated Registers
What does a control unit do?
Controls and coordinates the activities of the CPU, directing the flow of data between the CPU and other devices.
What are buses?
A bus is a set of parallel wires connecting 2 / more components of a computer (typically consists of 8/16/32/64 lines)
What are the three types of buses?
- Address
- Data
- Control
What is a control bus and what does it do?
The control bus is one of the three busses of the system.
The control bus controls most of the system. It gives commands to the system and hardware of the computer. These commands are:
Read - A single line that when active (logic zero) indicates the device is being read by the CPU
Write - A single line that when active (logic zero) indicates the device is being written by the CPU
Byte enable - A group of lines that indicate the size of the data (8, 16, 32, 64 bytes)
Transfer ACK - Delivers information that the data was acknowledged (read) by the device
Bus request - Indicates a device is requesting the use of the (data) bus
Bus grant - Indicates the CPU has granted access to the bus
Interrupt request - A device with lower priority is requesting access to the CPU
Clock signal - The signal on this line is used to synchronize data between the CPU and a device
Reset - If this line is active, the CPU will perform a hard reboot
What is a data bus and what does it do?
The data bus is one of the three buses of the system. The data bus takes data to/from the memory to/from the CPU. This bus is bidirectional, which means that data is able to travel both ways. The amount of data a data bus is able to transfer at once is called bandwidth. Typical bandwidths are 32 bits, with newer computers being able to handle 64-bit and 96-bit data paths. This means that up to 96 bits of data can travel through a data bus every second.
What is an address bus and what does it do?
An address bus is a computer bus architecture used to transfer data between devices that are identified by the hardware address of the physical memory (the physical address), which is stored in the form of binary numbers to enable the data bus to access memory storage
State all registers in the CPU and what they do
Current Instruction Register(CIR)- The register that stores the instruction that is currently being executed
Program Counter(PC)- The register that holds the address of the next instruction to be executed.
Memory Address Register(MAR)- The register that stores the address of the date, or the address of where the data will be sent to
Memory Data Register(MDR)- The register that holds the data being transferred to and from the immediate memory
Accumulator(ACC)- The register which holds an intermediate value in mathematical and logical calculations. This is all for a very short amount of time
Explain the Fetch decode execute cycle - 6 marks
Fetch: Contents of Program Counter / PC are transferred to Memory Address Register / MAR
the address bus is used to transfer this address to the main memory
The transfer of content uses the data bus
Contents of addressed memory location loaded into the Memory Data Register /
MDR
Increment (contents of) Program Counter / PC A. at any part of fetch process
after transferring PC to MAR
Increment Program Counter / PC and fetch simultaneously
Contents of MDR copied to CIR
Decode:
Decode instruction held by the (Current) Instruction Register / (C)IR
The control unit decodes the instruction
Instruction split into opcode and operand
Execute:
If necessary, data is fetched
If necessary, data is stored in memory
The opcode identifies the type of operation/instruction to be performed (by the
processor)
Result (maybe) stored in register/accumulator
The operation (identified by the opcode) is performed by the processor. A. ALU
Status register updated
If jump/branch required Program Counter/PC is updated
Remember this for full marks in ANY FDE question
What is clock speed?
Generates signals switching between 0 and 1 to synch CPU operations. The speed is measured in Ghz - The more the better
What is a multi-core processor
A multi-core processor is a processor that consists of two processors linked together in an integrated circuit. A dual core is likely to have double the speed of a signle core (unless the app does not support multi core processors) - The more the better
What is Cache Memory
The cache is a small amount of expensive, fast memory inside the CPU - The more the better
What is pipelining how does it work and why is it useful?
Pipelining allows for the processor to start another process while the previous one is still being completed allowing for faster processing speeds, therefore, a higher clock speed.
What is the von Neumann machine?
In a von Neumann machine, the same data bus is used to transfer both data and instructions. The same word length is used for all memory, whether it holds data or instructions.
What is the Harvard Architecture?
Unlike the Neumann it has separate memories for instructions and data.
