RANDOM ACCESS MEMORY
The primary memory and temporary storage in a computer is called RAM.Get More Electrical Concept And Interview Questions By Using This Link
RAM stands for Random Access Memory. RAM is stored on the mother board in modules called DIMMs (Dual Inline Memory Module). DIMM is a dual inline module because it has two independent rows pf the pins one on each side. DIMM module has a 168, 184, 240 or 288 pins. In DIMM RAM is installed on the mother board memory slots. Mother board can have a various number of memory slots the average mother board will have between 2 and 4 memory slots. In order to run a computer the data or program to be loaded in the RAM first.
The data or program first stored on the hard drive from the hard drive is loaded into RAM. Once it’s loaded into RAM CPU can access data to run the program. If memory is too low then the computer will run slowly. This happens some other data has to be cared slower hard disk to compensate the low memory.
Instead of data going from RAM to CPU it has to do extra work going back to hard disk. When it happens it slows down the computer to solve this problem all you need into increase the RAM in computer and increasing the memory. More data can be added in the faster RAM without need constantly accessing the slower hard disk. As a result it wills faster performing the computer. This is why computer is with more RAM performing faster with a computer less RAM.
RAM requires constant electrical power to store data. If power is turned off then data is erased.
There are different types of RAM are available. They are as follows
Dynamic RAM (DRAM)
DRAM is memory that contains capacitors. Capacitors acts like small bucket stores electricity and these capacitors hold the bit information such as 1 or 0 because computer reads the data’s 1 and 0. The capacitors have to be refreshed with electricity constantly because capacitor does not hold the change very long. They constantly leak this refreshing is called dynamic. The capacitors have to dynamically refresh often otherwise it will forget the information that are holding.
Synchronous Dynamic RAM (SDRAM)
This type of memory is used in RAM DIMMs. SDRAM also has capacitors like DRAM, but difference between SDRAM and DRAM is basically speeding.
- DRAM operates asynchronously either the system clock. It basically means it runs slower than the system clock because their signals are not coordinated with it.
- SDRAM operates synchronously with system clock. Which is faster than DRAM? All signals are tied to the system clock for a better controlled timing.
The DIMM are different memory sizes it ranges from 128 megabytes to 32 gigabytes per DIMM.
SDRAM is also rated for different speeds.
The term 64 or 32 bit data path refers to the number of data that are transferred in one clock cycle.
The more bits are transfer in one cycle the faster the computer DIMM have 64 bit data path. This means they can transfer 64 bits data at a time.
The priority DIMM older is called SIMM. SIMM has a 32 bit data path. That means it can transfer 32 bit data path at a time. That’s why dim is faster than SIMM because they can transfer twice the amount of data per cycle.
A single bit or one bit of data is the smallest form of data that the computer reads because in computer world computer can understand 1 or 0 which is represented a single bit of data.
There is also term called byte.
8 bits = 1 byte
If DIMM is 64 bit data path that means it has 64/8 = 8 bytes wide bus.
DSRAM is rated at different speeds.
The old SDRAM in 1990s could be labelled PC-100. 100 refer maximum speed which operates 100 MHz speed. SDRAM comes 64 bit marginal it has 8 bytes wide bus because 64/8 = 8.
The figure of bandwidth 100 MHz * 8 bytes = 800 Mb/s. so the bandwidth of PC-100 is equals 800 Mb/s. other words PC-100 RAM can transfer data maximum 800 Mb/s
SDRAM marginal label PC-133
133 MHz = the speed at which it operates, 8 byte wide bus.
133 MHz * 8 bytes = 1066 Mb/s
The total bandwidth of PC 133 is 1066Mb/s. technically 133 times = 1064 but 1066 is accurate because actual clock speed is 133.3333 * 8 = 1066.
Another type of memory is called Hard RAM. This was developed by Rambus link, later developed as RIMM.
RIMM (Rambus Inline Memory Module)
RIMM has 184 pins and 100 pins similar to DIMM with bottom notches are near the center of module. In 1999 RIMM was breakthrough in the speed of memory but quickly failed behind the advance of technology in DIMM.
When hard RAM debuted in 1999 RDRAM is speed was 800 MHz which is considerably faster than SDRAM at 133 MHz at that time but even though faster than SDRAM. Hard RAM had only 2 byte wide bus compared to SDRAM has 8 bytes wide bus. If we multiple by speed of hard RAM 800 MHZ * 2 BYTES = 1600 Mb/s.
Technically increased process and bus speed have gone faster new RAM technology was developed it keep up faster speed of computer newer technology called DDR.
DDR (Double Data Rate)
The basically DDR is does sends double the amount of data in each clock signal compared to non-DDR.
Non DDR is a single data rate RAM using only rising edge clock signal to transfer data. But DDR uses both the rising edge and falling edge of clock signal to transfer data. This gives DDR to and ability to send twice the amount of data.
Difference between DDR and Non DDR
Even though system clock signal at same speed for both RAM modules. DDR module sends the twice the amount of data. Even if we increase the clock speed the DDR is still faster than the non-DDR.
DDR is labelled differently than non-DDR RAM. DDR may include both the clock speed and the total between its names by the clock speed its name like PC-133. When 133 equals clock speed DDR includes total bandwidth also PC-2700.
333 are clock speed 2700 is the actual bandwidth. 333 MHz * 8 bytes = 2700 Mb/s.
New technology succeed in DDR-2
DDR-2 is faster than DDR because it allows for higher bus speed and effectively sends twice the amount of data than DDR and also uses less power than DDR. DDR 2 has 1 240 pin compared to DDR has 184 pins. DDR 2 is labelled like DDR with small difference like DDR2 – 800 MHz and PC- 6400. It includes ‘2’ in the label by this it can be identified.
DDR3 is twice faster than DDR2 also uses less power than DDR2. It has 240 pins the notches in DIMM are different places. It can be placed DDR3 in RAM slot made for DDR2. In fact Mother Board can support certain type of memory. The DDR1, DDR2, DDR3 and DDR4 all are placed in same mother board.
Fourth generation DDR4
It has 288 pins and also uses less power. It offers a higher range of speed in DDR3. DDR4 – 4266 MHz PC 4 – 3100 which has a bandwidth of 3400 Mb/s.