2. Table of Content
Introduction
How Does It Work?
History of RAM
Types of RAM
Limitations of RAM
3. Introduction
RAM ( Random Access Memory)
is the internal memory of the
CPU for storing data, program
and program result.
RAM is a read/write memory which stores data until the
memory is working as soon as the machine is switched off
data is erased.
RAM is a volatile memory, which means it does not store
data or instructions permanently.
RAM is generally located on the motherboard. Data in the
RAM can be accessed randomly but it is very expensive.
4. How Does It Work?
When the computer first starts a program it sends an address
to RAM to begin retrieving that program. The RAM address
just consist a series of 1’s and 0’s representing ‘ ON’ and ‘ OFF’
wire.
RAM does not do anything with that address until the CPU
turns on the “SET” or “ENABLE” wire. If the enable wire is
turned ON the RAM automatically senses the data
corresponding to that address back to the CPU, that data is
then processed by the CPU accordingly.
5. History of RAM
The first form of RAM came about in 1947 invented by
Williams Tube. It was used in CRT, and the data was stored as
electrically charged spots on the face.
The second type of RAM was magnetic-core memory
inverted in 1947 by Frederick Viehe . It made of tiny metal
rings and wires connecting to each ring .
The RAM which we know today, as solid-state memory, was
invented by Robert Dennard in 1968 at IBM Thomas J Watson
Research Centre. It is specifically known as dynamic random
access memory (DRAM) .
6. Types of RAM
RANDOM ACCESS
MEMORY
STATIC RANDOM
ACCESS MEMORY
DYNAMIC
RANDOM ACCESS
MEMORY
7. Static Random Access
Memory
• SRAM holds data in a static form , as long as the memory has
power.
• SRAM chips use a matrix of 6-transistors and no capacitors.
Transistors do not require power to prevent leakage, so SRAM
need not be refreshed on a regular basis.
• There is extra space in the matrix, hence SRAM uses more
chips than DRAM for the same amount of storage space,
making the manufacturing costs higher. SRAM is thus used as
cache memory.
8. Dynamic Random Access
Memory
• DRAM, unlike SRAM, must be continually refreshed in order
to maintain the data.
• All DRAMs are made up of memory cells, which are
composed of one capacitor and one transistor.
• DRAM is used for most system memory as it is cheap and
small.
9. Difference Between SRAM &
DRAM
SRAM DRAM
It is a static memory as it does not
need to be refreshed repeatedly.
It is a dynamic memory as it needs to
be refreshed continuously or it will
lose the data.
Its memory cell is made of 6
transistors and no capacitors.
Its memory cell is made of one
transistor and one capacitor.
It is more expensive than DRAM. It is less expensive than SRAM.
It has a lower access time, e.g. 10
nanoseconds. So, it is faster than
DRAM.
It has a higher access time, e.g. more
than 50 nanoseconds. So, it is slower
than SRAM.
10. Limitations of RAM
• One of the biggest drawback of RAM is that it is a volatile
memory. This means that whenever the computer is switched
off all the data that was stored in the RAM is lost.
• Another limitation of RAM is space limitation. The cost per bit
for RAM is high as compared to ROM , because of this reason
it is not used for mass storage.
