The System

Question 1

What is a bus hierachy

Answer 1

Systems can have more than one bus connected together - a bus hierachy dictates which is the most important (system bus) and which are more secondary

Question 2

what is a bus bridge

Answer 2

A way to connect a bus to one or more other busses - can work like an adaptor meaning a bus only needs to know how to connect to the bridge - rather than multiple other types of bus

Question 3

Why is raw bus bandwidth never achieved in practice

Answer 3

Because bus arbitration (PCI controller chip deciding what device is up next for control of the bus) and bus turnaround - handing over control

Question 4

What are some ways to improve bus bandwidth

Answer 4

Block transfer - transferring multiple words in a single transfer (however this monopolises the system bus and makes it less reactive) - other devices have to wait

Question 5

What is a buffer?

Answer 5

busses different speeds - producer/consumer

Question 6

A bus system has a protocol overhead of 5 cycles, a bus width of 32 bits, and a bus frequency of 200 MHz.

a. Calculate the data transfer rate for single transactions
b. Calculate the data transfer efficiency with block sizes of 16 bytes.

Question 7

What is disk storage

Answer 7

non volatile, rewritable, 2d, magnetic

Question 8

what is seek time and how do we reduce it ?

Answer 8

amount of time to find data

smaller tracks, more platters (means smaller read/write heads), faster rotational speed

Question 9

What is a Solid State Drive/advantages thereof?

Answer 9

Array of memory chips
Controller makes the SSD look like a disk - but it’s not mechanical in the same way as a disk
fast access time - normally only needs a digital lookup
able read multiple files ‘interleaving’

Question 10

ssd disadvantage

Answer 10

wear - reading & writing memory cells wears them

helped by wear levelling - writing to different parts of memory to spread out the wear

Question 11

What is Ethernet and what is CSMA/CD

Answer 11

An ethernet is a network that connects different devices together using a wired connection

CSMA/CD is a method/protocol used by Ethernet controllers to manage multiple devices sharing use of the internet and resulting possible collisions

Carrier Sense - checking what/if other devices are using the connection
Multiple Access - More than one device is connected
Collision Detection - can’t have more than one device using the system at one time, if that happens devices will stop for a random period of time each, then try again