RAM : Difference Between DRAM, SDRAM, DDR, DDR2, DDR3, DDR4

RAM : Random Access Memory :

RAM : Random Access Memory - Difference Between DRAM, SDRAM, DDR, DDR2, DDR3, DDR4

We're going to talk about one of the most important parts of a computer and we're going to be talking about primary memory or temporary storage and this is called RAM Ram stands for random access memory RAM is stored on the motherboard in modules that are called dims dim stands for dual inline memory module a dim is a dual inline module because it has two independent rows of these pins one on each side a dim memory module has either 168 184 240 or 288 pins and then the dim is installed on the motherboard in the memory slots.

A motherboard can have a various number of memory slots the average motherboard will have between 2 and 4 of them in order for data or program to run on a computer it needs to be loaded into Ram first so the data or program is first stored on the hard drive then from the hard drive it's loaded into Ram and once it's loaded into Ram the CPU can now access the data or run the program now a lot of times if the memory is too low it might not be able to hold all the data that the CPU needs and when this happens then some other data has to be kept on the slower harddrive to compensate for the low memory so instead of the data going from RAM to the CPU it has to do extra work by going back to the hard drive and when this happens it slows down the computer so to solve this problem all you need to do is increase the amount of RAM on a computer and by increasing the memory more data can be loaded into the faster Ram without the need of constantly accessing the slower hard drive and the result is a faster performing computer so this is why a computer with more RAM performs faster than a computer with less RAM ram requires constant electrical power to store data and if the power is turned off then the data is erased Ram also comes in different types such as dynamic RAM or DRAM.

DRAM : (Dynamic Random Access Memory)

DRAM is memory that contains capacitors a capacitor is like a small bucket that stores electricity and it's in these capacitors that holds the bit of information such as a 1 or a 0 because that's how computers read data which is ones or zeros and because DRAM has capacitors they have to be refreshed with electricity constantly because capacitors do not hold a charge for very long they constantly leak and this refreshing is where we get the name dynamic the capacitors have to be dynamically refreshed.

SDRAM : (Synchronous Dynamic Random Access Memory)

SDRAM stands for synchronous DRAM and this type of memory is what is used today in RAM DIMMs. SDRAM also has capacitors like DRAM but the difference between SDRAM and DRAM is basically speed the older DRAM technology operates asynchronously with the system clock which basically means that it runs slower than the system clock because it's signals are not coordinated with it but SDRAM runs in sync with the system clock which is why it is faster than DRAM all the signals are tied to the system clock for a better controlled timing so as stated before RAM is stored on the motherboard in modules that are called dims and these dims come in different memory sizes today they range anywhere from 128 megabytes to 32 gigabytes per dim SDRAM is also rated at different speeds but before we talk about the speed of ram we need to define some things first now the term 64 or 32 bit data path refers to the number of bits of data that are transferred at a time or in one clock cycle the more bits that are transferred in one clock cycle then the faster the computer will be now dims have a 64 bit data path which means that they can transfer 64 bits of data at a time now prior to dims there was an older Ram module called a sim and Sims had a 32-bit data path which means they can transfer data at 32 bits at a time so that's why dims are faster than Sims because they can transfer twice the amount of data per clock cycle because dims transfers 64 bits of data at a time compared to Sims which transfer 32 bits of data at a time now a single bit or one bit of data is the smallest form of data that the computer reads because in the computing world a computer only understands ones and zeros which is represented by a single bit of data.

There is also the term byte and eight bits is equal to one byte so if a memory dim is ready to have a 64-bit data path then that means that it has an 8 byte wide data path or bus because 64 divided by 8 equals 8 SDRAM is rated at different speeds for example a stick of old SDRAM way back in the late 1990s could be labeled PC 100 the 100 equals a maximum speed at which it operates which is 100 megahertz and since SDRAM only comes in 64-bit modules as we discussed earlier it has an 8 byte wide bus because 64 divided by 8 equals 8 so to figure out the total bandwidth of PC 100 you multiply 100 megahertz times 8 bytes which equals 800 megabytes per second so the total bandwidth of PC 100 equals 800 megabytes per second so in other words PC 100 Ram can transfer data at a maximum rate of 800 megabytes per second so an SDRAM module labeled PC 133 you multiply 133 by 8 which equals 1066 so the total bandwidth for PC 1 33 equals 1066 megabytes per second now technically 133 times 8 actually equals 1064 but 1066 is accurate because the actual clock speed is 130 3.3333 times 8 which is rounded off to 1066 another type of memory was called our DRAM which was developed by Rambis Inc and they developed the rim which stands for Rambus inline memory module rims have 184 pins and looks similar to dims with the exception that the bottom notches are located in the center of the module in 1999 rims were breakthrough in the speed of memory but has quickly fallen behind due to the advancement of Technology in dims when our dream debuted in 1999 it ran at 800 megahertz which was considerably faster than SDRAM which ran at 133 megahertz at that time but even though it was a lot faster than SDRAM our DRAM only had a two byte wide bus compared to SDRAM which had an 8 byte wide bus so if you multiply the speed of our DRAM which was 800 megahertz times the bus width which was 2 bytes you would get a total bandwidth of 1600 megabytes per second.

RAM : Random Access Memory - Difference Between  DRAM, SDRAM, DDR, DDR2, DDR3, DDR4

DDR : (Double Data Rate)

Technology increased and processor and bus speeds have gotten faster a new ram technology was developed to keep up with the faster speeds of computers this newer technology was called DDR which stands for double data rate and that's basically what DDR does it sends double the amount of data in each clock cycle compared to non DDR non DDR or single data rate Ram uses only the rising edge of the clock signal to transfer data but DDR uses both the rising and falling edges of the clock signal to send data which gives DDR the ability to send twice the amount of data.

Difference between DDR and non DDR:

So even though the system clock is pulsating at the same speed for both RAM modules the DDR Ram module can send twice the amount of data since it takes advantage of both the rising and falling edges of the clock signal so even if we speed the clock up and make it go faster the DDR Ram will still send twice.

The amount of data compared to the non DDR Ram. ddr is also labeled differently than non DDR Ram DDR Ram may include both the clock speed and the total bandwidth in its name so instead of just including the clock speed in its name like PC 133 where 133 equals the clock speed DDR includes the total bandwidth also so for example a DDR dim labelled DDR 333 PC 2700 the 333 is the clock speed and the 2700 is the actual total bandwidth so 333 megahertz times 8 bytes equals 27 hundred megabytes per second which is where we get the name PC 2700.

DDR2 : (Double Data Rate 2)

DDR2 is faster than DDR because it allows for higher bus speeds and effectively send twice the amount of data than DDR and it also uses less power than DDR a DDR to dim has 240 pins compared to DDR which has one hundred and eighty four pins ddr2 is labeled just like DDR but with a small difference for example a DDR to dim could be labeled ddr2 800 PC to 6400 and the difference is the two right after the DDR and the two right after the PC so this is how you can identify ddr2 memory by using its label and right after ddr2 is ddr3.

DDR3 : (Double Data Rate 3)

DDR3 is twice as fast as ddr2 and it also uses less power than ddr2 and just like ddr2 ddr3 also has 240 pins but the notches in the dims are in different places so you can't put a ddr3 DIMM in a ram slot made for a ddr2 in fact motherboards are made to support a certain type of memory so you can't mix DDR 1 2 3 or 4 on the same motherboard an example of ddr3 would be ddr3 1600 PC 3 12800 and the fourth generation of DDR SDRAM is ddr4 ddr4 DIMMs have 288 pens and like its predecessors it also uses less power than the previous generation of DDR.

DDR4 : (Double Data Rate 4)

DDR4 also offers a higher range of speed than ddr3 such as ddr4 4266 PC 434 100 which has an incredible maximum bandwidth of 34,000 100 megabytes per second our circumstances where memory data corruption cannot be tolerated for example in servers servers are meant to be up and running at all times and some servers cannot afford being offline for any reason such as servers that control financial data emergency medical data or government data these servers cannot go down for any reason and that's why some Ram modules have ECC.

ECC : (Error Correcting Code)

It stands for error correcting code and what ECC does is that it detects if the data was correctly processed by the memory module and makes a correction if it needs to you can tell if a ram module has ECC by counting the number of memory chips on the module and a standard non-ecc them it will have eight memory chips but in an ECC memory module it will have nine memory chips now most Ram modules today are non ECC and this is because of the advanced and technology that has minimised memory errors and has made non ECC Ram more stable but as stated before ECC memory is mostly used in servers because servers need to be up and running at all times and using ECC memory is just an extra precaution to guard against any memory errors.

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