What is RAM? RAM in details | Each and every question answered.
RAM- Random Access Memory
It was fitted on a board in modules that are called DIMMs(Dual Inline Memory Module). A DIMM is a dual inline memory module because it has two independent rows of pins, one on each side. A DIMM has either 168, 184, 240 or 288 pins.
DIMM is installed on the motherboard in the memory slots. A mother can have various number of memory slots. Normally a motherboard has 2 to 4 slots.
We know the programs or data are stored permanently on a hard drive or secondary storage device. In order to run a program, it needs to be loaded into RAM first. Then CPU accesses the data or programs from RAM.
Normally increasing the RAM will run the computer faster.
RAM is a volatile memory. It need constant supply of power to store data. When power off everything stored on it erases. RAM are of different types.
Some of them are discussed below.
As per data storage type we can divide as : static RAM and dynamic RAM. Your computer may have both the RAMs. static RAM is faster and expensive compared to dynamic RAM. A static RAM holds data till power is on. But in dynamic RAM to keep the data till power on, the memory controller reads the data and write it back. This process is known as refreshing and this happens thousand times per second making RAM slower compared to static RAM. Therefore static RAM is used to create the CPU’s speed-sensitive cache, while dynamic RAM forms the larger system RAM space.
Now we will discuss different types of Dynamic RAMs.
1. DRAM : Dynamic RAM. It contains capacitors and these capacitors stores the bit of information either 0 or 1. Capacitors have to be refreshed constantly because they can’t hold charge for long time. This refreshing technique named it dynamic.
2. SDRAM : Synchronous Dynamic RAM . This type of RAMs used today in DIMMs. It also have capacitors but it is faster than DRAM because it operates Synchronously with the system clock.
Now RAM are available from 128 MB in size to 32 GB in size. RAM also available in different speeds. Before knowing the speed of ram we should know what is 32 bit and 64 bit.
The term 32 or 64 bit data path refers to the number of bits of data that are transferred in 1 clock cycle. DIMMs have a 64 bit data cycle. Means they can transfer 64 bits of data at a time. Previously we are using SIMMs which have a 32 bit data module but now a days that is discontinued.
A single bit or 1 bit of data is the smallest form of data that the computer reads, that may be a 0 or 1. 8 bit forms a byte. If we are saying a DIMM has 64 bit data path, means it has a 8 byte wide data path or bus.
If it was written PC-100 on a RAM, what is the bandwidth of that RAM or what is the data transfer rate of that ram? 100 MHz = The speed at which it operates. DIMM = 8 byte wide bus. So bandwidth = 100 X 8 = 800 MB/s So PC-100 RAM can transfer data at a maximum of 800 MB in one second.
As the technology advanced we used DDR (Double Data Rate) Technology which sends double the data as compared to non-DDR technology DIMMs. Means at the same time, DDR sends the data twice while non-DDR send the data only once. DDR named different as compared to non-DDR Ram. It may include both the clock speed and the total bandwidth in its name. It has 184 pins. It was written on my RAM DDR-400MHz and PC3200U. In this case 400 MHz is the speed and the band width = 400 * 8 = 3200 which was already mentioned as PC3200U.
A new technology came called DDR2. It is faster than DDR because it allows for higher bus speed and effectively sends twice the data of DDR and uses less power. It has 240 pins. DDR2 may be named as DDR2-800MHz PC2-6400.
Again a new technology came as DDR3. It is two times faster than DDR2 and also uses less power than DDR2. It has also 240 pins like DDR2 but bottom notches are in different places. A DDR3 may be named as DDR3-1600MHz PC3-12800.
The fourth generation is DDR4. It has 288 pins. It offers a higher range of speed and uses less power. It may be named as DDR4-4266MHz PC4-34100. Means its transfer rate is 34100 MB/s.
A mother board is made to support a certain type of RAM so you can not interchange DDR with DDR2 or DDR3 or vice versa.
In servers like financial server, emergency medical servers or Govt servers data corruption cannot be tolerated. So some memory modules has ECC (Error Correcting Code). ECC RAMs can detect if the data was correctly processed by the memory module and makes a correction if it needs to.
Difference between ECC and Non ECC RAM
Non-ECC RAM has 8 memory chips, whereas ECC RAM has 9 memory chips. Most RAM today are non-ECC because the advanced technology minimized the memory errors making the Non-ECC RAM more stable.