The document provides an overview of digital memory, explaining the data storage capacity of devices and detailing types of memory such as primary, secondary, SRAM, DRAM, and ROM. It discusses various memory technologies like SRAM's static nature and high speed, as well as DRAM's need for refreshing and its various types including DDR and SDRAM. The document also includes information about memory modules and differences between memory types.

1. Memory

2. Introduction
The data storing capacity of a digital
device is known as memory.
Memory of device like empty pages of
note book.
Memory devices enables us to retrieve the
stored data from the memory.
Examples are HDD, CD, DVD, pen drive,
floppy disk, memory cards.

3. Types of memories
Memory
Primary
memory
Main
memory
Secondary
memory

4. Main memory
RAM
ROM
HARD
DISK

5. Primary memory
The essential memory to work with
computer is known as primary memory.
It is also called volatile memory or
temporary memory.
Volatile memory stores the data
temporarily, it looses the data as soon as
the system power supply turned off.
RAM is the good example for volatile
memory.

6. RAM
Random Access Memory.
It is a semi conductor memory where CPU
and other hardware devices can read and
write data.
It stores the data temporarily.
That is why it is called as volatile memory,
once if we switch off the computer it
looses the data.

7. Types of RAMs
RAM
SRAM
DRAMVRAM

8. SRAM
 Static RAM.
 It is a one type of semi conductor memory.
 It stores the data until the power supplied to the
system.
 SRAM uses 4 to 6 transistors for each memory cell.
 If more no of transistors present in the cell, the cells
do not require refreshing data frequently.
 Refreshing a cell means rewriting data in a cell.
 SRAM is faster in accessing data, due to the speed it
acts like cache memory.

9. Cache Memory
It is a type of SRAM, enables the
processor to send data at a very high
speed.
Two types of cache memories.
External cache memory.
Internal cache memory.

10. External Cache Memory
It is placed between main memory and
micro processor (CPU), it stores the data
temporarily.
It is also called as L2 cache.
CPU
RAMCache

11. Internal Cache Memory
It is associated with the micro processor.
Helps to increase the processing speed of
processor.
CPU
Cache
RAM

12. DRAM
 Data stores in memory cells in DRAMs.
 Each memory cell contains a pair of transistors
and a capacitor.
 Memory cell is referred as a bit of data.
 The life time of the data in DRAM is very short, it
is approximately 15 ms.
 The memory cells of DRAM are refreshed by the
DRAM controller.
 DRAM controller is a hardware component that
helps the DRAM works like the SRAM.

13. Types of DRAMs
DRAM

14. FPMDRAM
Fast Page Mode DRAM.
This is standard DRAM, accessed through
a technique called paging.
Paging enables faster access to all the
data with in a given memory.
This technology was popular on 32-bit
wide memory systems on 486 processors.
It will not support Pentium processors, 64-
bit memory devices.

15. EDODRAM
Extended Data Out DRAM.
It is a type of asynchronous DRAM. It is also
known as Hyper Page Mode DRAM.
It’s data transfer rate is approximately 264 MB
per second.
It is faster than normal DRAM.
It is 6% faster than FPMDRAM.

16. RDRAM
Rambus DRAM is the fastest computer
memory.
It sends the data frequently on the data
bus.
It’s data transfer speed is 800 MHZ.
The high performance work stations and
servers uses RDRAM.
The video memory on the graphic cards
uses RDRAM.

17. SDRAM
 Synchronous DRAM.
 It synchronizes the memory speed with the CPU
clock speed.
 The speed of the SDRAM depends on the speed
of the processor.
 It is faster then SRAM, DRAM, FPMDRAM,
EDODRAM and VRAM.
 The data transfer speed of SDRAM is measured
in nanoseconds and MHZ.
 It works with a speed of 133 MHZ.

18. Modules in SDRAM
There are two modules of SDRAMs.
2 - Clock SDRAM 4 – Clock SDRAM
Each clock signal controls two
different DRAM chips.
Each clock signal controls
four different DRAM chips.
Used by older versions of
computers.
Using by latest computers.

19. Types of SDRAMs
It is the latest version
of SDRAM.
Double Data Rate
SDRAM.
Data transfer rate of
DDR is faster than
SDRAM. It is twice the
speed of SDRAM.
DDR consumes less
power.
DDR It is a type of
synchronous dynamic
access memory that
can transfer four words
of data in each clock
cycle.
Quad Data Rate
SDRAM.
It has separate read
and write ports that
can operate
simultaneously
QDR

20. Types of DDR
DDR 266 DDR 333 DDR 400 DDR2 533
DDR2 667
It is one of the
cheapest DDR
memories.
Available in the
market.
It is meant for the
users, those who
uses powerful
applications such
as video
processing soft
wares, latest
games etc.
It is recommended
for the some of the
latest mother
boards with at
least P4 2.8 GHZ,
or above.
DDR2 memory
chips runs at the
speed just double
the DDR
SDRAMs.

21. Differences between DDR and DDR2
Factor DDR DDR2
Data Bus 64 bits 64 bits
Data Rate 200/266/333/400 MHZ 400/533/667 MHZ
Frequency 100/133/166/200 MHZ 200/266/333 MHZ
density 128 MB to 1 GB 256 MB to 4 GB
Voltage 2.5 Volts 1.8 Volts

22. Memory packages
Memory package is a small circuit board
that contains memory chips.
The installation main memory on to the
computer depends on memory packages.

23. Types of memory packages
SIMM DIMM SODIMM RIMM
Single In – line
Memory Module.
Dual In - line
Memory Module.
Small Outline
Dual In – line
Memory Module.
Rambus Inline
Memory Module.

24. SIMM
 It is a small circuit board designed to hold memory chips.
 Various SIMM packages are available based on the
number of pins it contains.
30 – pin package 72 – pin package
The capacities of a 30 – pin SIMM
package are 256 KB, 1 MB, 2 MB, 4
MB, 8 MB and 16 MB RAMs.
It contains 2, 4, or 8 data chips per
module.
It has a data bus width of 8 bits with
9 bit parity.
Parity checks the accuracy of data
transmission.
The capacities of a 72 – pin SIMM
package are 1 MB, 2 MB, 4 MB, 8
MB ,16 MB, 32 MB, 64 MB and 128
MB RAMs.
It contains 2, 4, 8 or 16 data chips
per module.
It has a data bus width of 32 - bits
with 36 - bit parity.

25. ROM
Read Only Memory.
It stores the data permanently. It stores
the system configuration.
Lithium ion battery will supply continues
power supply to the ROM.
It is a non volatile main memory.

26. Different types of ROMs
ROM
PROM EPROM EEPROM

27. Other memories
0
1
2
3
4
5
6
7
8
9
10
physical memory
logical memory
virtual memory
Flash memory
Cache memory

28. Physical memory
Physical memory is the total amount of
memory installed in the computer.
E.g. RAM, ROM

29. Logical memory
Logical memory enables the user to use
large amount of memory to store data.
This enables the OS to arrange memory
into a logical manner.
The system maps the logical address to
real physical storage address.

30. Logical memory organization
 The computer’s main
memory is divided
into different
categories.
 Conventional memory
 Upper memory
 Extended memory
0
1
2
3
4
5
6
7
8
9
10
Extented
memory
Upper memory
Convential
memory

31. Conventional memory
This memory is also called as DOS
memory or BASE memory.
Size of the conventional memory is 640KB
and it is used by the DOS.
DOS can not use more than 640 KB for
most of it’s work.

32. Any doubts?
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