Signals

Question 1

What does an Interrupt Driven Architecture do?

Answer 1

Synchronisation between CPU and device controllers

HW or software can interrupt the CPU
- Transfer execution to a routine to handle the interrupt. (ISR)

Question 2

What are the different types of interrupts?

Answer 2

• Hardware interrupt via system bus, IO operation completion or error condition
• Software interrupts, known as traps
• Timer interrupts
• Hardware failure

Question 3

How does the OS Handle interrupts?

Answer 3

1. Program counter saved
2. Transfer control to ISR. This may include saving registers. ISR executes on per-thread kernel stack. Must then restore register state before return.
3. Transfer control back to original program

Question 4

What is the Interrupt Vector?

Answer 4

Interrupt vector indexed by device ID. Each element contains the address of the corresponding ISR

Question 5

What is Direct memory access?

Answer 5

Specialised processors for transferring data directly between memory and IO devices.

Transfers whole blocks at a time.

CPU only interrupted when block transfer completed.