DLD

1. MEMORY HIERARCHY
A SOLUTION FOR MODERN DAY COMPUTING

2. MEMORY:
“The Impression, Reminiscence and Souvenir of an
existence, is called Memory.”
Or
“The ability to collect and recollect data, is called
Memory.”

3. MOORE’S FIRST LAW:
“The number of transistors
per square inch on a dense
integrated circuit doubles
every two years.”

4. ROCK’S LAW (MOORE’S SECOND LAW):
“The cost of a semiconductor
chip fabrication plant doubles
every four years.”

5. THE PARADOX OF MEMORY:
The Ideal Memory:
Zero Access Time
Infinite Capacity
Zero Cost
Infinite Bandwidth
Realistic Memory:
Faster = Expensive
Bigger = Slower
Quality = Expensive
Higher Frequency =
More Ports = Expensive

6. MEMORY HIERARCHY:
At any given time, data is copied between only two
adjacent levels:
– Upper level: In the direct access to processor.
(Smaller, faster, uses more expensive technology)
– Lower level: In the indirect access to processor.
(Bigger, slower, uses less expensive technology)

7. IMPACT OF MEMORY HIERARCHY
For Computer Processing: If it worked for Cars:
•3,00,000 mph
•20,00,000 mpg
•4.19 Rupees per Car
•3,500x Performance
•90,000x Energy efficient
•60,000x Lower cost

8. LEVELS OF MEMORY HIERARCHY:

9. HIERARCHY MANAGEMENT:
Registers <-> Memory by compiler
Cache <-> Memory by the hardware (CPU)
Memory <-> Disks by the Hardware
(RAM) and OS
Virtual Memory by the Operating
System (OS) and
Program

10. PRIMARY MEMORY:
“The upper level volatile
memory, directly
accessed by processor, is
called Primary Memory.”
Example: Cache & RAM
SECONDARY MEMORY:
“The lower level non-
volatile memory, indirectly
accessed by processor, is
called Secondary Memory.”
Example: ROM & USB Flash

11. VIRTUAL MEMORY:
Virtual memory is a feature of an operating system
(OS) that allows a computer to compensate for
shortages of physical memory by temporarily
transferring pages of data from random
access memory (RAM) to disk storage. That Portion
of disk storage is referred as Virtual Memory or
Paging Files.

12. NEED FOR VIRTUAL MEMORY:
1. Before the development of the virtual memory
technique, programmers in the 1940s and
1950s had to manage directly two-level storage
such as main memory or RAM and secondary
memory in the form of hard disks or earlier,
magnetic drums.
2. Enlarge the address space, the set of addresses
a program can utilize.
3. Virtual memory might contain twice as many
addresses as main memory.

13. VIRTUAL MEMORY (PAGING)
Page table
Address Space
Page table
Address Space
Physical
Memory

14. WHAT IS OFFLINE MEMORY?
The term offline memory is referred to a secondary
storage medium that is non-volatile and whose data cannot
be accessed by the computer once removed. It must be
physically inserted into a system every time a users wants to access or edit
data. Offline storage can be any type of internal or external storage that
can easily be removed from the computer.

15. PORTABLE MEMORY
Any offline storage that is removable and needs to be
plugged in to read/write data and plugged out without
effecting any fundamentals of the machine, is called portable
memory.
Portable memory plays a vital role in the data transfer and
specially in making backups for privacy or security concerns.
Examples of portable memory are USB drive, SD Cards,
Floppy disks, Tape drives and CDs/DVDs or Blu-ray.