lab 8

Q1

What is the purpose of each of the following buses???

ISA

Allows for additional expansion cards to be added, like a network card, ISA is a slave to PCI

PCI

This is a faster smaller and faster version of ISA, it allows for more things like graphics cards and much more

SCSI

Used to connect to secondary storage, however modern SSDs can use PCI

USB

Connects to external devices

Q2

Name all the buses
  1. The top bus is the memory bus
  1. The one below that is the PCI bus
  1. The one on the left is the SCSI and USB buses respectivly
  1. The bottom bus is the ISA bus
Name devices that could be connected to each of the buses
PCI
  • Graphics card
SCSI
  • HHD
  • CD drive
USB
  • keyboard
  • mouse
ISA
  • Network card
  • Video card
  • Sound card

Q3

What is the purpose of the north and south bridge???

North bridge

Connects devices directly to the CPU, this is extremely quick

South bridge

Connects devices that are slightly slower, like keyboard and mouse

Q4

What Is the difference between synchronous and asynchronous buses???

Synchronise

  • Continuous stream of of bytes
  • Clocked
  • No handshake required

Asynchronous

  • One byte or one char at a time
  • Un-clocked
  • Handshake needed for synchronisation with receiver

Q5

Why are interrupts needed within a modern computer?

Answer

Without interrupts say the user pressed on something on a application, the user may have to wait for the computer to complete its current process, before the what happed to their mouse can be computed.

Investigate each of the steps below and explain what each is doing and why it is important

1. Determine the source of the interrupt
2. Resolve priorities
3. Disable further interrupts
4. Save PC and enter Interrupt Service Routine (ISR)
5. Service interrupt
6. Re-enable interrupts
7. Restore PC and exit back to previous task.

Answer
  1. To ensure that the hardware associated with the interrupt actually caused the interrupt
  1. To know which interrupt must be run first
  1. Make sure that the current interrupt does not get disturbed
  1. Save the point we are at in the current process and store it for later
  1. Compute what is necessary for the interrupt
  1. Allow interrupts
  1. Continue where we where in the process mentioned at the top

Investigate and explain what the PC and ISR are and why they are needed when handling
interrupts

Answer

The program counter is set to the start of the ISR

The Interrupt Service Routine (ISR) is the software that invokes a response to the interrupts

Investigate how interrupts interface with the Operating System

Answer
  • Interrupts will block the current process being run
  • They will invoke a part of the operating system

Are there any alternatives to interrupt handling?

  1. Outline how it/they work.
  1. Describe what type of devices they would be used for
  1. Describe what type of computer system they would be found within