Static and dynamic memories

The current technological revolution around the world has made the world faster with the
advancements in sophisticated computer devices. Computer, as a digital machine, enables people
to work faster than ever before. The memory of this device is a great feature of this digital tool.
RAM, Random Access Memory is the primary tool of data storage that is inserted in the
integrated circuit while data can be accessed in any sequence or randomly. Thus it is termed
RAM or Random Access Memory.
The journey of dynamic and static RAM was initiated in 1960s which can readily
developed in 1970s. Now a days the technology is much more user friendly. RAM is further
divided into three types:

• Dynamic RAM (DRAM)

• Static RAM (SRAM)

• Non-volatile RAM (NVRAM = RAM + Battery)
but we will discuss only first two i.e. (DRAM and SRAM).
Dynamic RAM is the most common memory used now a days. Inside of the RAM chip
there is a memory cell that holds one bit of information and is divided into further two parts: a
transistor and a capacitor. The capacitor holds the bit of information as a state of 0 or 1 and the
transistor acts as a switch that lets the control circuitry on the memory chip that reads the
capacitor or change its state. The capacitor is like a small bucket that stores the electrons in it. To
store 1, bucket gets filled with electrons and to store 0 buckets gets empty. The problem with the
capacitor’s bucket is that it has a leak and in a matter of few seconds a full buckets becomes
empty. Therefore they need to be recharged continuously in order to work properly and because
of this reason it has been given the name Dynamic RAM. This refreshing phenomenon is time
consuming as well.
In static RAM a flip-flop holds each bit of a memory. A flip-flop memory cell takes 4 to
6 transistors along with the wiring. Due to this reason they draws current all the time and gets
warm easily, therefore, they cannot be packed together tightly. They do not require any
refreshing method though, therefore, they are very fast memory chips.

1. 1
Data Logic and Design

Syed Ammar Ali
Aqdas Hassan
Static and Dynamic memories

2. Random Access Memory (RAM)
•Random-access memory  (RAM) is a type
of computer data storage. A RAM device
makes it possible to access data in random
order, which makes it very fast to find a
specific piece of information.
–These are volatile, switch the machine off and the
contents in this form of memory are lost
•There are two main types of RAM
–Dynamic RAM (DRAM)
–Static RAM (SRAM)
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3. Random Access Memory (RAM)
•Static RAM (SRAM)
–Memory behaves like Latches or Flip-Flops
–Data remains stored as long as power applied
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4. Random Access Memory (RAM)
•Dynamic RAM (DRAM)
–Charged or discharged capacitor
–Memory lasts only for a few milliseconds
–Data must be refreshed periodically by reading and
rewriting
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5. Working Of DRAM
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6. Working of DRAM
•DRAM store data by using Capacitor. Every
capacitor store one bit of data in the form of
charge and every one bit section is called cell as
shown in the figure.
•According to diagram shown below bit line
potential is high when the potential of word line
becomes high then the transistor behave like a
close switch then the capacitor starts charging.
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7. Working of SRAM
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8. Comparison between Static and
Dynamic RAM:
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Static RAM Dynamic RAM
Six to eight MOS transistors are
necessary for a Static RAM.
Three to four transistors are
required for a Dynamic RAM
Static RAM it is not possible to
refresh programs.
Dynamic RAM memory can be
deleted and refreshed while running
the program
Data is stored in flip flop level in
Static RAM.
Data is stored as a charge in a
capacitor in Dynamic RAM
Possesses more space in the chip.Possesses less space in the chip.
It is used to Create speed- sensitive
cache.
It is used to create larger RAM
space system.
It is 4 times more expensive and
consumes high power.
It is 4 times less expensive and
consumes less power than static.
It takes less time for accessing data
or information than DRAM.
It takes More time for accessing
data or information than SRAM.

9. Conclusion:
With all thing mentioned, the discussion
can be concluded by saying that Dynamic RAM
is slower than Static RAM, but it has a
refreshing option which makes it more viable.
Static RAM is costly and takes more spaces
than Dynamic RAM, but is faster than the other.
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10. T
hank
Y
ou
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