Third generation semiconductor memories provide improvements over earlier magnetic-based computer memories. There are two main types of semiconductor memory - RAM and ROM. RAM allows reading and writing and is used for temporary data storage, while ROM only allows reading and is used for permanent storage. Over time, new technologies like DRAM, SRAM, EEPROM, Flash memory were developed with improvements in speed, density, power consumption and non-volatility. Research continues into developing even more advanced memory technologies.

1. THIRD GENERATION
SEMICONDUCTOR
MEMORIES

2. OVERVIEW
• WHAT IS MEMORY?
• MEMORIES USED IN EARLIER GENERATION OF
COMPUTERS
• WHAT ARE SEMICONDUCTOR MEMORIES?
• DIFFERENT TYPE OF SEMICONDUCTOR
MEMORIES
• DISADVANTAGES
• SEMICONDUCTOR TECHNOLOGIES
• CONCLUSION

3. WHAT IS MEMORY?
Memory refers to the physical devices used to store programs
(sequences of instructions) or data on a temporary or permanent basis
for use in a computer or other digital electronic device.

4. MEMORIES USED IN EARLIER
GENERATION OF COMPUTERS
• FIRST GENERATION computers used vacuum tubes as
switching device and magnetic drum for memory.
• SECOND GENERATION computers magnetic-core memory
Magnetic Drum Magnetic Core memory

5. WHAT ARE SEMICONDUCTOR
MEMORIES?
Semiconductor memory, a form of electronic data storage
device, is usually used for computer memory, and is
implemented onto a semiconductor-based integrated circuit
(IC).

6. DIFFERENTTYPE OF SEMICONDUCTOR
MEMORIES
Electronic semiconductor memory can be split into two main
types or categories, according to the way in which the
memory operates:
• RAM - Random Access Memory
• ROM - Read Only Memory

7. SEMICONDUCTOR TECHNOLOGIES
There are various types of RAM and ROM available. These arise
from the variety of applications and also the number of
technologies available.
• PROM
• EPROM
• EEPROM
• Flash memory
• DRAM
• SRAM

8. PROM (PROGRAMMABLE READ
ONLY MEMORY)
• Data can be written only once.
• It consists of arrays which can be fused according to required
data pattern.
• Data is stored as charge on capacitor.

9. EPROM(ERASABLE
PROGRAMMABLE READ ONLY
MEMEORY)• Memory can be programmed and then erased at later time.
• Data is erased by exposing silicon to ultraviolet light.
• To enable this to happen there is circular window present in
EPROM.

10. EEPROM(ELECTRICALLY ERASABLE
PROGRAMMABLE READ ONLY
MEMORY)
• Uses electric voltage to erase data
• Same characteristics as EPROM

11. FLASH MEMORY
• A development of EEPROM.
• Non volatile.
• Data written and erased in blocks
• Therefore it uses programming voltages at level which are
available within the electronic equipment.

12. DRAM(DYNAMIC RANDOM
ACCESS MEMORY)
• Type of RAM.
• Uses capacitor to store each bit of data.
• Level of charge on capacitor determine whether the data bit is
0 or 1.
• Needs to be refershed periodically.

13. SRAM(STATIC RANDOM ACCESS
MEMORY)
• Unlike DRAM data need not be refreshed again and again.
• Faster read and write times than DRAM.
• Cycle time is also shorter.
• Consumes more power, expensive,less dense.

14. There are many developments going on in semiconductor
technologies to make memories more efficient, some of these are
as follows:
• TRAM
• ZRAM
• SDRAM
• MRAM
• P-RAM/PCM
• FRAM
• VRAM

15. TRAM(THYRISTOR RANDOM
ACCESS MEMORY)
• Type of DRAM.
• Invented and developed by T-RAM semiconductors.
• Combine strenght of DRAM and SRAM (high density and high
speed.)
• It exploits the electrical property negative differential
resistance.
• Highly scalable and has storage density higher than standard 6
transistor SRAM.

16. ZRAM(ZERO CAPACITY RAM)
• Invented and developed by innovative silicon.
• Based on floating body effect of silicon on insulator
technology.
• It is claimed that ZRAM offers same access speeds as standard
6 transistor SRAM but it uses only 1 transistor.

17. SDRAM(SYNCHRONOUS DRAM)
• Runs at faster speed than DRAM.
• Synchronised with processor clock.
• Is capable of keeping 2 sets of memory address open
simultaneously.

18. MRAM(MAGNETO RESISTIVE
RAM)
• Non volatile.
• Uses magnetic charges to store data.
• Requires low power for active operation.

19. PRAM(PHASE CHANGE RAM)
• Based on the phenomenon of phase change of a form of
chalcogenide glass from amorphous state to poly crystalline
state.This is used to store data.

20. FRAM(FERROELECTRIC RAM)
• Similar to DRAM.
• Instead of dielectric layer FRAM contains ferroelectric layer of
lead zirconate titanate.
• Non volatile.
• Consumes ultra low power, single cycle write speed and has
gamma radiation tolerance.

21. VRAM(VIDEO RAM)
• Also called MPDRAM(Multi port DRAM).
• Normally VRAM has 2 independent access points instead of 1
allowing CPU and graphics processor to access RAM
simultaneously.
• Located on graphics card and comes in variety of formats.
• Used for video adapters or 3D accelerators.

22. DISADVANTAGES
• Reliability issues for RAMs, SRAMs and DRAMs.
• Hot-carrier degradation effects
• space radiation environment

23. CONCLUSION
With the requirements for ever larger, faster and lower power
memories always increasing, this area of technology will
remain one of the most dynamic in the electronics industry.

24. THANK YOU