computer systems

What does the CPU stand for?

Central Processing Unit

What is the purpose of the CPU?

To process data and instructions by carrying out the FDE cycle.

What happens during the fetch-decode-execute cycle?

Fetch	The next instruction is fetched from memory and stored in the processor
Decode	The instruction is decoded
Execute	The instruction is carried out and then the cycle repeats

What are the common components of the CPU?

• ALU (Arithmetic Logic Unit)

• CU (Control Unit)

• Cache

• Registers

What is the function of the ALU?

To perform mathematical and logical operations.

What is the function of the CU?

• To co-ordinate the processor by issuing signals to other components

• To control the flow of data around the processor

• To decode instructions (in the CIR)

What is the function of cache?

To temporarily store data + instructions that the processor frequently accesses.

What is the key feature of the Von Neumann architecture?

Data and programming instructions are stored in the same format (binary), in the same memory (primary - specifically RAM)

What are the registers the CPU uses in the Von Neumann architecture?

• PC (Program Counter)

• MAR (Memory Address Register)

• MDR (Memory Data Register)

• CIR (Current Instruction Register)

• ACC (Accumulator)

What is the purpose of the PC?

The function of the PC is to store the memory address of the next instruction to be fetched from primary memory.

What is the purpose of the MAR?

The function of the MAR is to store the memory address of the current instruction that is to be fetched from primary memory or the memory address to which data is to be transferred to.

What is the purpose of the MDR?

The function of the MDR is to store the data found at the memory address stored in the MAR or data which is to be transferred to primary memory.

What is the purpose of the ACC?

The function of the accumulator is to store the data being processed + the results of processing.

What characteristics of the CPU affect its performance?

• Cache size

• Clock speed

• Number of Cores

What is cache memory?

A small amount of high-speed RAM built directly within the processor.

How can increasing cache size improve CPU performance?

Cache memory is closer to the CPU than RAM so data + instructions can be accessed accessed at a faster rate.

Increasing cache size means more data and instructions can be stored in cache memory and accessed faster.

What is clock speed?

The number of fetch-execute cycles a CPU can perform per second, measured in Gigahertz (GHz).

3GHz → 3 million FDE cycles per second

How can increasing clock speed improve CPU performance?

Increasing clock speed means the CPU can perform and complete more FDE cycles faster, therefore more instructions can be processed faster.

What is a core?

A complete set of CPU components that is able to complete its own FDE cycles.

How can increasing the number of cores improve CPU performance?

By increasing the number of cores, the CPU can process more instructions as each core is capable of completing its own fetch-decode-execute cycles.

What is an embedded system?

A computer system built into a larger device to perform a few specific tasks.

What are the characteristics of an embedded system?

• Perform a few select tasks

• Tasks are pre-programmed + stored in ROM

• Small in size

• Low cost

What is an example of an embedded system?

Washing Machine