Memory

Question 1

What’s the primary memory?

Answer 1

System: registers, cache, main memory, virtual and directly accessed by CPU

Question 2

What’s the secondary memory?

Answer 2

Hard-drives

Question 3

Where must data be transferred to in secondary memory?

Answer 3

Main memory when needed

Question 4

What’s off-line memory?

Answer 4

They back up process and transport data

Question 5

How many bytes are in a bit?

Answer 5

8 bites

Question 6

What’s computer memory?

Answer 6

Temporary storage area and it holds data and programs that CPU needs

Question 7

What’s a pigeonhole analogy?

Answer 7

Back in WW1, pigeons were used to deliver letters across fronts

Question 8

How much does a storage location hold?

Answer 8

One word, like an 8-bit computer, holds 8-bit words

Question 9

Define ‘‘address’’

Answer 9

Using bytes to locate to memory and a single address can space between RAM and ROM

Question 10

What’s the RAM?

Answer 10

Random Access Memory it’s assessed by CPU, it read and writes and it’s volatile memory where a state is lost as soon as power is cut

Question 11

What’s a Static RAM?

Answer 11

It’s a fast, retaining state which has a high cost per bit and is used for registers, caches, buffers in I/O.

Question 12

Where’s the SRAM?

Answer 12

RAM in embedded systems

Question 13

What’s a Dynamic RAM?

Answer 13

Opposite to SRAM, which is slower, its bits are stored in capacitors as charges, low cost per bit and is used for large memory unit and it also needs refreshing because it discharges after some time

Question 14

There are two types of DRAM, name them

Answer 14

SIMM and DIMM

Question 15

What’s a SIMM?

Answer 15

A single inline memory module which had 32-bit bus width

Question 16

What’s a DIMM?

Answer 16

A dual inline memory module which as 64-bit bus width and can store up to 32 GB.

Question 17

What’s DDR and what does it do?

Answer 17

Double Data Rate, it transfers data on both rising and falling edges of the block signal and 2 signal per cycle compared to SDR.

Question 18

Why do we need higher ‘‘confidence’’ in RAM?

Answer 18

Due to error-rates like we would need extra chips to handle the traffic on popular servers or government databases

Question 19

What’s an LP-DDR RAM?

Answer 19

It’s used in mobile devices, LP stands for low power, its temperature is defined by refresh rate, it’s slower and smaller than regular DDR

Question 20

Why use Virtual Memory?

Answer 20

We use it when the computer has little physical memory available, it’s slower than main memory.

Question 21

What’s a ROM?

Answer 21

Read-Only Memory, it’s non-volatile and it’s used to start up your computer like BIOS.

Question 22

What’s a cache?

Answer 22

A small amount of entire memory space is being accessed at any given time, values are accessed repeatedly

Question 23

Temporal locality?

Answer 23

Values tend to be accessed repeated at nearby times

Question 24

Sequential locality?

Answer 24

Same sequences tend to be re-accessed in same orders

Question 25

Spatial locality?

Answer 25

Values nearby in memory tend to be accessed together

Question 26

Level 1 Cache

Answer 26

Data cache to store data only

Question 27

TLB

Answer 27

Translation lookaside buffer (TLB) cache for virtual memory

Question 28

What’s a block in cache?

Answer 28

Copies of several contiguous words from memory

Question 29

What’s a tag in cache?

Answer 29

Address or other ID describing which memory is copied in the block

Question 30

What’s a dirty bit in cache?

Answer 30

Logging whether data was changed

Question 31

What’s hit or miss?

Answer 31

Requested data is found not found, it consists of rate time and miss penalty

Question 32

What’s a victim in cache?

Answer 32

Cached data to be thrown out to make room for new data

Question 33

What’s a hash function?

Answer 33

It maps big data to smaller ones, usually not possible to recover original data

Question 34

What’s a disadvantage of directed hash function?

Answer 34

That it can’t keep multiple uses of addresses in the cache if they share the same hash

Question 35

What are there other mapping algorithms?

Answer 35

Full associative and hybrid

Question 36

What’s a magnetic disk drive?

Answer 36

To read and write data to disk surfaces, platter spins at high speeds, 5400 RPM - 15000 RPM

Question 37

What’s the meaning of Access Time?

Answer 37

It seeks time it takes for an arm to position itself over desired tracks

Question 38

What impacts the data transfer?

Answer 38

The size of the data

Question 39

What’s RAID?

Answer 39

Redundant Array of Independent Disks

Question 40

What does RAID do?

Answer 40

Makes hard discs more resilient to failure