CPC - Hardware

What did Von Neumann realize about data & programs?

They are indistinguishable and can use the same memory.

What kind of processor does Von Neumann architecture use?

A single processor.

What is the sequence of operations in Von Neumann architecture?

Fetch – Decode – Execute.

What component stores small amounts of data for fast access?

Registers.

What are registers?

Smallest unit of storage; allow fast data transfer.

What are General Purpose Registers used for?

Temporarily store data values and processed results.

What are Special Purpose Registers?

Registers with a particular function (e.g. PC, MDR, MAR).

What does the Program Counter (PC) do?

Holds the address of the next instruction to fetch.

What does the Memory Data Register (MDR) do?

Holds data fetched from memory.

What does the Memory Address Register (MAR) do?

Holds the address of the memory cell to be accessed.

What does the Accumulator (ACC) do?

Holds values being processed by arithmetic/logical operations.

What does the Index Register (IX) do?

Stores a value to modify an address (indexed addressing).

What does the Current Instruction Register (CIR) do?

Holds the fetched instruction for decoding/execution.

What does the Status Register do?

Holds results of comparisons, errors, or intermediate arithmetic results.

What does the Arithmetic & Logic Unit (ALU) do?

Performs arithmetic & logical operations.

What does the Control Unit (CU) do?

Fetches, decodes, and directs execution of instructions.

What is Immediate Access Store (IAS)?

Memory directly accessible by the processor.

What is the system clock?

Synchronizes all components using timing pulses.

What are buses?

Parallel wires for data transfer between computer components.

What does the Data Bus do?

Bidirectional, carries data/instructions.

What does the Address Bus do?

Unidirectional, carries memory addresses.

What does the Control Bus do?

Bidirectional, transmits control signals.

What is clock speed?

Number of pulses per second (measured in GHz).

How does increasing clock speed affect performance?

Increases performance, but limited by heat generation.

What is bus width?

Number of lines in a bus; affects simultaneous data transfer.

How does bus width affect performance?

Wider bus = more bits transferred at once = higher speed.

What is cache memory?

Stores frequently used instructions for faster CPU access.

How does increasing cache size affect performance?

Reduces CPU wait time, increases performance.

What does number of cores mean?

Number of processors in a CPU chip; more cores = multitasking = better performance.

What is a port?

Hardware interface between CPU/device & peripherals.

What does USB port do?

Connects both input and output devices.

What does HDMI port do?

Connects output devices (e.g. monitors), carries audio & video.

What does VGA port do?

Connects output devices (video only, no audio).

What does the PC do during fetch?

Holds the address of next instruction.

What happens to PC during fetch?

PC address copied to MAR, PC incremented.

Where is the instruction loaded from and to?

Loaded from memory to MDR, then to CIR.

What happens during decode?

Opcode and operand are identified.

What happens during execute?

CU sends signals to carry out instruction.

What does "MAR ← [PC]" mean?

Copy value from PC to MAR.

What does "PC ← [PC] + 1" mean?

Increment PC by 1.

What does "MDR ← [[MAR]]" mean?

Load value from memory at address in MAR into MDR.

What does "CIR ← [MDR]" mean?

Copy value from MDR to CIR.

What do square brackets [ ] mean?

Value currently in register.

What do double square brackets [[ ]] mean?

Value stored at the address in the register.

What is an interrupt?

A signal seeking processor's attention.

When are interrupts checked?

At end of F-E cycle for current instruction.

What happens if interrupt is high priority?

Registers saved on stack, PC loaded with ISR address, ISR executed, then registers restored and execution resumes.