RAM: (Random Access Memory).
1) RAM is the main memory of the computer (primary memory)
2) RAM is used as random access memory.
3) RAM is used as temporary working space of the CUP and other components of the PC .
4) It holds the operating system, programs, and data that are currently in use.
5) Temporary memory stored on chips, such as RAM which can be installed on SIMM, DIMM, and RIMM slots inside the computer.
6) The information stored in RAM is volatile.
7) RAM speed is measured in ns (anon seconds).
Types:
STATIC RAM:
Ø Static ram stores date in electronic circuit called FlipFlop.
Ø It uses 6 Transistors in order to store in memory all.
Ø It stores the data till the power is on.
Ø S-RAM normally reserved for speed. Critical functions such as system cache.
Ø It is about 4-5 times faster than D-RAM.
DYNAMIC RAM:
Ø D-RAM is used as the main or system memory of a pc that that stores the operating system application programmes and data while they are running.
Ø It uses one transistor and one capacitor for a memory call.
Ø Comparing to S-RAM data access is slow.
Ø It stores the date only for few milliseconds after it has to be refreshed and charge gain.
FPM RAM :( Fast Page Mode)
1) Normally D-RAM required a row and column address to be sent for each access to memory cell.
2) FPM offers speed improvements by sending the row address just for money access to memory.
EXTENDED DATA OUTPUT D-RAM:- (EDO D-RAM)
Ø EDO D-RAM works similarly to FPM D-RAM
Ø Compared to FPM D-RAM EDO D-RAM provides 90% improvement in reading the data.
Ø The improvement can be done by continuing to output data from one address while simultaneously setting up access request for next one.
Ø This allows faster micro processor to manager the time more efficiently
SD-RAM: (Synchrony Data RAM)
Ø It is designed to run at mother board clock speed . Synchronization the memory speed with CPU clock speed.
Ø The speed of SD-RAM depends upon the CPU BUS.
Ø It is faster then SD-RAM, D-RAM, and Memories.
Ø It runs with an average speed of at 133MHz which is about three times faster than FPM RAM and twice as fast as EDO RAM. Most Pentium or Celeron systems purchased in 1999 have SDRAM.
Ø It is also Synchronization with system clock.
Ø SD-RAM transfers data on rising edge of clock signal where as DDR transfers data on doth edges of clock signal
Ø That’s why data transfer rate of DDR is faster then SD-RAM
Ø It is almost twice the speed of SD-RAM.
RAMBUS DYNAMIC RAM:
Ø IT has the clock speed of 800MHz
Ø It has bus width of 2 bytes.
Ø It can achieve speed up to 1.6 G bps.
SIMM:-
Ø SIMM generally come in 30 pin (or)72 pin (or) 68 pin
Ø It generally come in various capacities ranging from 512 KB.
Ø IT supports 32 bit Date width RAM
Ø It support FPM,EDO
DIMM:-
Ø It support 64 bit date RAM
Ø It has 168 pin SD-RAM.
Ø It has 240 PIN DDR2
Ø It has 184 PIN DDR1
Ø It support SD RAM,DDR1,DDR2,RDRAM
SODIMM :-( Small out Line)
Ø It is use in Laptops computers.
| SRAM | DRAM |
| Stores data till the power is switched off . | Stores data only for few milliseconds |
| Uses a set of transistors for each memory cell | Uses a single transistor and capacitor for each memory cell |
| Does not refresh the memory cell after each reading of the transistors. | Needs to refresh the memory cell after each reading of the capacitor |
| Data access is faster . | Data access is slower |
| Consumed more Power. | Consumed less power. |
 More expensive than DRAM. | Less expensive than SRAM. |
RAM Specifications:
| RAM type | Pins | Width | Usage |
| SD RAM | 168 | 64 bit | Older and slower type. No use. |
| Ram bus RAM | 184 | 16 bit | Advanced RAM. Only used for very few Pentium 4’s with certain Intel chipsets. |
| DDR RAM | 184 | 64 bit | A faster version of SD RAM. Used both for Athlon and Pentium 4’s. 2,5 Volt. |
| DDR2 RAM | 240 | 64 bit | New version of DDR RAM with higher clock frequencies. 1,8 Volt. |
