paper 2: system architecture computer sci

Why does the CPU need a heat sink?

It is so powerful and produces so much heat so it needs its own dedicated fan to keep it cool.

What does the CPU stand for?

Central Processing Unit

What is the CPU?

The circuitry that controls the manipulation of data.

What are the three main components in the CPU? Include the acronym as well.

ALU - Arithmetic/Logic Unit

CU - Control Unit

Registers

What is the ALU?

The circuit that perform the operations on data.

Arithmetic: operations like adding/subtracting.

Logic: evaluated (false or true).

What is the CU?

The circuits coordinating the activities of the CPU.

What are the Registers?

Quick, small stores of data within the CPU.

Why are registers in the CPU seen as efficient?

They have a temporary storage making it faster, they don't have to keep going back and force to memory.

What is Von Neumann Architecture?

We can break our systems down into 4 components: memory, ALU, CU and input/output.

What is the stored program concept?

Instructions to be executed are stored in the memory (alongside the data) as binary values.

How are instructions executed in the Von Neumann model?

They are executed sequentially - one instruction AT A TIME is fetched from memory → CPU.

What will happen if you have a very fast CPU but there is a slow connection between memory and CPU?

You get a Von Neumann bottleneck, so you cannot access data and instructions at the same time.

What does the Clock provide?

Timing signals to synchronise circuits. Like a pulse.

Why is there a clock in the CPU?

CPU’s are designed to operate at a specific frequency - and the system clock is raised to this rate by the processor, giving the clock speed (Hz)

What does the CPU need a certain amount of per instruction?

Clock ticks/cycles per instruction.

What is the fetch decode execute cycle?

Fetch: the next instruction is retrieved by the CPU from Main Memory.

Decode: instruction broken down to individual components to determine the instruction and what data is used.

Execute: CU activated the necessary circuity/data transfers. The output of this stage is stored in a register, data may be read/written to main memory during this.

What is Main Memory?

Is what is directly accessible by the CPU: RAM, ROM and (sometimes) Cache, but in practice usually refers to RAM.

Are registers in main memory?

No.

What are the two types of memory?

Volatile and Non-Volatile.

What is Volatile memory?

Memory loses it's data when power is lost. (Like an unsaved game file)

What is Non-Volatile memory?

Retains it's data when power is lost. (Like a game save file)

Is RAM volatile or non volatile?

Volatile

Is ROM volatile or non volatile?

Non volatile

Is cache volatile or non volatile?

Volatile

Would data that would be permanently kept (hard drives ect) be volatile or non volatile?

Non-Volatile.

Is non volatile memory faster than volatile memory?

No, volatile memory is faster.

What is main memory also known as?

Primary storage

What does RAM stand for? Why?

Random Access Memory. Reading takes roughly the same time regardless of location

Describe RAM.

quick read/write times.

Function is to load open programs/operating system data currently in use from the slowe secondary storage. So it can be accessed directly by the CPU. It is like the tabs open on your screen.

What does ROM stand for? Why?

Read Only Memory. It can only be read, so data can't be changed once programmed.

What is Cache?

A type of memory that stores copies of frequently used data.

How is cache much faster than RAM?

Stores copies of frequently used data.

What main memory type has low capacity?

Cache (mb)

Why is CPU catch closer to the processor?

It is checked before RAM in fetch stage, to see if it's in there already.

What is clock speed measured in?

Hz

The faster the clock speed cycles are, the __________ can be executed per second.

More instructions

What does cache exist for?

It speeds up the operation of the fetch stage.

What happens to instructions when the cache is larger?

More instructions can be accessed faster.

What does having multiple cores in the CPU allow?

Multiple instructions to be executed simultaneously.

What's happens to performance as more cores increase?

The performance increases if everything else is optimised.

What is secondary storage?

Any memory devise not connected to the CPU.

Why is secondary storage needed?

So there is long term storage (non volatile) available.

What is optical storage?

• Binary data stored as variations of height on the disks surface

• To read data: light is shined on disk, light hits pits and lands

• Data is written with a lazer burning pits into disk (like vinyls kinda)

What are the features of Optical Storage? (Evaluate)

Small capacity (most CDs < 1GB)

Fairly reliable + durable but can be damaged easily (scratched)

Good portability (easy to transport/carry).

What is magnetic storage?

Use read/write heads that contain electromagnets.

Parts of surface are magnetised (1)/demagnetised(0) and heads control this and read what state they're in.

Features of magnetic storage (evaluate)

Large capacity and cheap.

Usually reliable but not durable (moving parts)

Generally not very portable.

Can be noisy and generate heat.

What is solid slate storage?

Form of flash memory so non mechanical.

Consists of digital circuits that retain data which can be changed.

What are the features of solid state storage (evaluate)

Very fast for storage but expensive.

Reliable as they aren't mechanical.

Don't need defragmentation.

Generally have smaller capacity than magnetic.

Silent

Very durable.

What is cloud storage?

Where data is stored on multiple servers in a remote location.

Serves use magnetic and now increasingly solid state storage.

Generally operates through web based API.

Features of cloud storage (evaluate)

Portable - accessed anywhere on internet. But means can't be used when no internet.

Always has backups, but could not be reliable.

Maybe cheaper for large companies (reduced energy costs) but likely to be expensive for small users.