Classifications of Locality of References Principles

Question 1

What is principality of locality

Answer 1

Principle of locality or locality of reference is the tendency of a processor to access the same set of memory locations repetively over a short period of time

Question 2

Types of locality

Answer 2

Temporal locality: Here a resource that is referenced at one point in time is referenced again soon afterwards

Spatial Locality: Here the likelihood of referencing a storage location is greater if a storage location near it has been recently refereence

Sequential Locality: Here storage is accessed sequentially, in descending or ascending order. This leads to memory hierachy

Question 3

What is memory hierarchy

Answer 3

Memory hierarchy is a structure that uses multiple levels of memories; as the distance from the CPU increases, the size of the memories and the access time both increases.

The faster

Question 4

Main memory is implemented from?

Answer 4

It is implemented from Dynamic Random Access Memory(DRAM)

Question 5

The level closer to the processor(caches) uses ?

Answer 5

SRAM

Question 6

Mention the levels in memory hierachy

Answer 6

CPU Registers
Static Random Access Memory
Main Memory
Local Disk
Remote Secondary Storage

Question 7

Describe CPU Registers

Answer 7

They are at the top most level of this hierarchy, the hold the most frequently used data.

The are very limited in number and are the fasters
They are often used by the CPU and the ALU for performing arithmetic and logical opertions, for temporary storage of data.

Question 8

What are registers

Answer 8

A register is a digital circuit with two basic functions: data storage and data movement.

Question 9

Types of registers

Answer 9

Parallel and serial registers

Different manner:
Serial-in/Serial-out
Parallel-in/serial-out
Serial - in / pararell-out
Universal parallel-in/ parallel out

Question 10

Describe SRAM

Answer 10

SRAM is a type of RAM that holds data in a static form, that is, as long as the memory has power.

SRAM stores a bit of data on four transistors using tow cross-coupled inverters.

Question 11

What is Main Memory or DRAM

Answer 11

Dynamic random access is a type of memory that is typically used for data or program code that a computer processor needs to function.

Question 12

Pro of DRAM

Answer 12

Simple design, speed and low cost in comparison to other types

Question 13

Con of DRAM

Answer 13

Volatility and high power consumption

Question 14

Describe Local Disks

Answer 14

A local drive is a computer disk drive that is installed directly within the host or the local computer

Question 15

Describe Remote Secondary Storage

Answer 15

This includes Distrubuted File System(DFS) and online storage like cloud.

The storage area is vast with low cost but larger access time.

Question 16

Differences between SRAM and DRAM

Answer 16

SRAM stores data till power is supplied while DRAM stored data only for few miliseconds irrespective of the power supply.

Uses nearly 6 transistors for each memory cell. Uses single transistor and capacitor for each memory cell.

Do not referesh the memory cell. Refereshing circuiting is need

Faster data access. Slower access
Consume more power. Low power consumption.
Cost per bit is high. Comparatively lower cost

Question 17

How does data transfer between level work

Answer 17

Through blocks

Question 18

What is block

Answer 18

The minimum unit of information that can be either present or absent

Question 19

What is a memory unit

Answer 19

It is a collection of semi-conductor storage cells with circuits to access the data stored in them.

The data stored in memory is done with words

Question 20

Why memory hierarchy

Answer 20

Fast storage techs cost more per byte and have less capacity
Gap betwen CPU and main memory speed is widening
Well written programs tend to exhibit good locality

Question 21

Elements of memory

Answer 21

Processor Memory: Present inside the CPU for high spped data access. This consist of small set of registers that act as temporary storage.

Primary Memory: Directly accessed by the CPU. All data must be brought inside the main memory before accessing them.

Secondary memory: This is the cheapest, larage and relatively slow memory component. The data from the secondary memory is accessed by the CPU only after it is loaded to main memory.

Question 22

What trade off among memory

Answer 22

Cost
Capacity
Access time

Question 23

What is hit

Answer 23

If the requested data is found in the upper levels of memory hierarchy

Question 24

What is miss

Answer 24

If the requested data is not found in the upper levels of memory hierarchy

Question 25

What is hit ration

Answer 25

It is the fraction of memory access found in the upper level.

Question 26

Formula for hit ration

Answer 26

Hit Ratio = Hit/(Hit+Miss)

Question 27

Formula Miss rate

Answer 27

1 - hit rate

Question 28

What is hit time

Answer 28

The time requried for accessing a level of memory hierarchy, including the time needed for finding whether the memory access is a hit or a miss

Question 29

What is miss penalty

Answer 29

The time required for fetching a block into a level of the memory hierarchy from the lower level, including the time to access, transmit , insert it to new level and pass the block to the requestor

Question 30

What is bandwidtg

Answer 30

The data transfer rate by the memory

Question 31

What is Latency or access time

Answer 31

Memory Latency is the length of time between the memory reciept of a read request and its release of data corresponding with the request.

Question 32

What is cycle time

Answer 32

It is the minimum time betwen requests to memory