Memory

Question 1

What is primary memory ?

Answer 1

Lives in the system bus address space directly accessible from the CPU

Question 2

What is secondary memory ?

Answer 2

Hard drives, Solid State Drives, All data must be transferred to the primary memory

Question 3

What is tertiary memory ?

Answer 3

Recent versions of Offline storage

Question 4

What is offline memory ?

Answer 4

Storage connected externally, via the I/O or manual insertion.

Question 5

What is primary storage made up of ?

Answer 5

consists of many storage cells, each cell can hold 1 bit. Each memory location can hold 1 word (16 bits).

Question 6

What are the three types of RAM?

Answer 6

RAM, Static RAM, Dynamic RAM

Question 7

What is Static RAM ?

Answer 7

bits stored in flip flops, fast, retains state, complex instructions, high cost. Used in registers and cache

Question 8

What is dynamic RAM ?

Answer 8

Bits stored in charge capacitors, slower than Static, discharges after some time, structurally simple, Low cost, used as the main bulk of the RAM

Question 9

What is a memory controller ?

Answer 9

Maps system addresses to one RAM module

Question 10

What is ECC RAM ?

Answer 10

Used for more confidence in RAM errors. Usually stores extra copies of data. Not commonly used as DRAM is good enough

Question 11

What is LP-DDR RAM ?

Answer 11

Low power, can shut down parts of the RAM that are not in use. Used in phones and laptops

Question 12

What is ROM ?

Answer 12

Limited number of write / erase cycles, non-volatile. used to store firmware

Question 13

What is the Cache ?

Answer 13

small amount of fast memory between the CPU and the DRAM

Question 14

What types of locality are there ?

Answer 14

Temporal locality – values tend to be accessed repeated at nearby time

Sequential locality – same sequences tend to be re-accessed

Spatial locality – memory addresses close to each other tend to be accessed together

Question 15

What types of the cache are there ?

Answer 15

Instruction cache and data cache

Question 16

What is the translation look aside buffer ?

Answer 16

A cache that stores the recent translations of virtual memory to physical memory

Question 17

What is a memory tag ?

Answer 17

Addresses or IDs that describe what memory is located on the block

Question 18

What is a block ?

Answer 18

sequence of bytes or bits

Question 19

What is a dirty bit ?

Answer 19

Tracks whether the block has bit modified

Question 20

What is hit / miss and vitcims ?

Answer 20

Hit / miss is whether the data is found or not
victim is the part of the cache which will be erased

Question 21

What is a hash function ?

Answer 21

Used to map data of arbritrary size to fixed size positions

Question 22

What makes up a hard disk ?

Answer 22

one or more rigid disks coated with magnetic material. magnetic heads mounted on moving arms for read / write.
platter spins at high speeds, each platter has tracks, each track into sections. data stored in the sectors.

Question 23

What is RAID architecture ?

Answer 23

More reliable way of using hard disks. RAID 1 = copy data across multiple disks. RAID 5 = Split file across multiple disks