CIE AS Computer Science Performance

What does the number of cores refer to?

The number of ALUs in a processor

Does 2 cores (dual-core) necessarily = x2 execution speed?

no

What needs to be done to make having multiple cores useful?

Software needs to be designed to utilise multiple cores

Typically CPUs will have cores in multiples of…

2

What can multiple cores cause?

Overhead, because having multiple cores requires communication between cores

What is overhead (in computing)?

Refers to the additional resources required to manage and execute processes which do not directly contribute to the actual work being done

What may make having multiple cores useless?

Memory access speed not matching the speed of the cores - cores may be ready to execute instructions, but if enough instructions are unable to be retrieved from the memory fast enough to allow all cores to continually process instructions, then having multiple cores is useless as some cores will not be doing any work and waiting for additional instructions to arrive

What is the advantage of having a number of cores?

Each core can independently carry out a process simultaneously

What does bus width refer to?

the number of bits that can be transferred via the address bus, data bus and/or control bus

What does a higher bus width mean?

An increased speed of memory access and overall computer system

What is clock speed?

the number of fetch-decode-execute cycles that can be conducted per second

What is clock speed measured in?

Hertz (Hz) e.g. 2.1 Ghz process = 2.1 billion FDE cycles per second

Do additional cores result in a perfectly multiple clock speed?

No due to hardware/software constraints

Where is cache memory?

between the CPU and RAM

What is the function of cache memory?

Holds frequently used instructions/data

Why is cache memory useful?

it allows the CPU to more quickly access data/information because it does not have to go all the way to RAM

Is RAM or cache memory faster?

cache memory