We will now discuss the different types of DRAM. DRAM stands for Dynamic Random Access Memory. DRAM is an essential part of any computing device. So whether you see a laptop, desktop, mobile, or any gaming console, you will find these DRAM inside all these devices.
Types of DRAM and their Generations
We will compare the different types of DRAM in terms of their speed or bandwidth, their packaging standards in which they are available, and also different types of DRAM and the applications in which they are used.
Now, if you see the different generations of DRAM, you will find an improvement in the speed and the reduction in power consumption in each generation. So if you see the ancient generation DRAM, they were the asynchronous DRAM.
It means that the RAM is not synchronized with the CPU clock. Now the disadvantage of these RAM types was that the CPU does not know the exact timing at which the data will be available from the RAM on this input-output bus. That problem has been overcome by the next generation of RAM, known as a Synchronous DRAM (SDRAM).
In the case of SDRAM, the RAM is synchronized with the CPU clock, and the advantage of SDRAM is that the CPU or, to be precise, memory controller knows precisely the timing or the number of cycles after which the data will be available on the bus. So CPU does not need to wait for the memory access, and because of that, we can increase the memory read and write speed.
Input Output Clock Frequency
The input-output clock frequency is when the data is being transferred between the RAM and the memory controller.
Internal Clock Frequency
The RAM’s internal clock frequency is the frequency used by the RAM for internal operations.
In the Synchronous DRAM case, the Input-Output Clock Frequency and the Internal Clock Frequency of the RAM are the same.
Suppose the RAM’s Internal Clock Frequency is 100 MegaHertz. In that case, the Input-Output Clock Frequency is also 100 MegaHertz. Generally, if you see this Synchronous DRAM, the operating frequencies in the range of 100 to 133 MegaHertz.
If you find the PC 100 on the SDRAM module, the Input-Output Clock Frequency is 100 MegaHertz. The data that is being transferred between these RAM and the memory controllers at the rate of 100 Mega transfer per second.
Data Transfer Rate
If this bus is 64 bit wide, then the data rate in terms of bits per second will be equal to 100 megahertz into 64 bits. If you convert it into the byte, it will be divided by the 8 bits: 800 MegaBytes Per Second (MBPS).
The synchronous DRAM module is operated at 3.3 volts. This SDRAM is also known as the single data rate SDRAM. Because it is transferred at the end of every rising gaze of the clock cycle in these RAMs.
If you see the next generation of synchronous DRAM, they are known as the DDR RAM because, in this DDR RAM, the data is transferred twice during the clock cycle, i.e., during the positive-negative edge. So in this way, the data is being transferred twice during each cycle, which is why it is known as a Double Data Rate or DDR SDRAM.
If you see these DDR RAM, different generations are starting from the DDR1 up to the DDR4. Nowadays, memory is used inside the desktop, laptop, or mobile, i.e., either DDR3 or DDR4 RAM.
Generations of DDR RAM
1. DDR1 RAM
The first generation of DDR RAM is known as DDR1 RAM. So compared to the SD-RAM here, the voltage has been reduced from 3.3 volts to 2.5 volts. In the DDR RAM case, the data is being transferred both during the raising and the falling gaze.
We can say that in a single clock cycle, instead of 1 bit, the 2 bits are being pre-fetched. So that is generally known as 2 bits pre-fetched. Now here in DDR1 RAM, the internal clock frequency and the Input-Output Clock Frequency are the same.
Generally, this DDR1 RAM is operated in the range of 133 Megahertz up to 200 MegaHertz. But if you see the Input-Output Bus data rate, it will be doubled compared to the clock frequency.
In the case of the DDR1 RAM, the data is transferred both during the raising and the falling gaze. Suppose if you’re operating these DDR1 RAM at 133 MegaHertz, then you will see the data rate as 266 Mega Transfer Per Second. If the bus frequency is 200 MegaHertz, then the data transfer rate will be equal to 400 Mega Transfer Per Second.
If the Input-Output Bus is 64 bits wide, then the data rate in terms of bytes per second will be equal to 3200 MegaBytes Per Second.
These DDR RAMs are generally denoted by the term DDR followed by the transfer rate of this RAM. And if you see a DDR1 module or DDR1 stick, then on that stick, you would find that the term is used as PC 3200. It means that the maximum speed or the maximum bandwidth achieved by this DDR1 RAM is 3200 MegaBytes Per Second.
2. DDR2 RAM
The second generation of DDR RAM is known as DDR2 RAM. DDR2 RAM is operated at 1.8 volts instead of 2.5 volts. If you see the internal RAM clock frequency, the internal RAM clock frequency is the same as the previous generation. The data rate is doubled compared to the last generation. This has been achieved by increasing the number of bits that has been pre-fetched during each cycle.
In this DDR2 RAM, instead of 2 bits, 4 bits are pre-fetched during each cycle. In the case of this DDR2 RAM, the internal bus width of this RAM has been doubled.
If the input-output bus is 64 bits wide, then the internal bus width of this RAM will be equal to 128 bits. So in this way, in a single cycle, we can handle a double amount of data. To handle the same amount of data, it should double the clock frequency of this input-output bus.
Internal Clock Frequency
Suppose, if this DDR2 RAM is operated at 100 MegaHertz internal clock frequency, then the input-output bus should have a clock frequency of 200 megahertz. In the case of this DDR RAM, data is transferred both during rising and falling age.
So it will double the data rate compared to the clock frequency, i.e., 400 Mega Transfer Per Second, and in terms of the DDR terminology, it can be written as DDR2 followed by the transfer rate. So suppose, if DDR 2 RAM is operated at 400 megahertz clock frequency, then the data rate will be equal to 800 mega transfer per second.
In terms of terminology, it is written as DDR2 800. If you see the DDR2 module on the module, it will be written as PC2 6400, which means the Bytes Per Second data rate.
3. DDR3 RAM
The third generation of DDR RAM is known as DDR3 RAM. In the case of DDR3 RAM, the voltage is further reduced from 1.8 volts to 1.5 volts. If you see RAM’s internal clock frequency, it is slightly improved compared to the last generation.
Internal Clock Frequency
But the data rate that you can achieve with the same frequency is being doubled compared to the previous generation. Because in the case of this DDR3 RAM here, the number of bits that are being pre-fetched is increased from 4 bit to the 8 bit or in a simple way the RAM’s internal data bus width has been increased two times compared to the last generation.
So in the case of this DDR3 RAM, suppose if the internal clock frequency is 100 MegaHertz and to match the data rate, the input-output bus should operate at four times the clock frequency 400 MegaHertz. The transfer rate that you will get will be equal to 800 Mega Transfer Per Second.
So in any DDR3 module, if you find a term that is DDR3 800 followed by PC3 6400, it means that this RAM is DD3 RAM, which is operated at 1.5 volts and the clock frequency of this RAM is 400 megahertz. The maximum transfer rate which can be achieved is 800 Mega Transfer Per Second. The maximum bandwidth of this RAM is 6400 MegaBytes Per Second.
4. DDR4 RAM
The fourth generation of DDR RAM is known as DDR4 RAM. Again, in this DDR4 RAM, the operating voltage has been reduced from 1.5 volts to 1.2 volts. Also, the number of bits in DDR4 RAM being pre-fetched is the same as the previous generation, i.e., 8 Bits Per Cycle.
Internal Clock Frequency
But the internal clock frequency of the DDR4 RAM has been increased. So if you are operating at 400 MegaHertz, then the clock frequency of this input-output bus should be four times, i.e., 1600 MegaHertz, and the transfer rate will be equal to 3200 Mega Transfer Per Second.
If you see the module, on the module, you will find the term, ie. PC4 followed by 25600 that is the speed in terms of MegaBytes Per Second. In terms of DDR terminology, you will find it as a DDR4 followed by 3200.
So far, whatever discussion we carried out, we have assumed that the input-output bus width is 64 bits. But if we increase this bus width, let’s say if you double this bus width, then the theoretical data rate we achieved would double. So whenever this RAM is used in such mode, then it is known as Dual Channel Mode.
So now suppose, if we have two options, let’s say one 8 GB DDR4 RAM which is used as a single channel mode and two 4 GB of DDR4 RAM’s which are used as a dual-channel mode. Then the bandwidth which can be achieved with this two 4GB of DDR4 RAM will be better compared to the single-channel 8GB of DDR4 RAM.
So far, We have seen different generations of these dynamic RAMs in terms of their speed and operating voltages. Now let us also see the different packages in which these dynamic RAMs are available. So significantly, the older generation of dynamic RAM was available in the dual inline package.
Single Inline Module
Then after the next generation of RAMs were available in the single inline module. So in the case of this single inline module, these memory chips are soldered onto the one PCB, and the pins are available on the single side of the PCB. That is a reason this packet is known as a Single Inline Module, as the pins are available only on one side of the PCB.
The single inline module can provide the data bus width of 32 bits. If you want 64 bits of the data bus, you need to connect the two single inline modules in a paradol.
Dual Inline Module (DIMM)
After the next generation of RAMs were available in the dual inline module or known as the DIMM. So in this Dual Inline Module, it is possible to have a 64-bit wide data bus, and in this case, the pins were available both in front and the back of the PCB, and that is the reason it is known as the Dual Inline Module.
If you see the different generations of DDR RAMs, they were available in the DIMM module. But all the modules have a different number of pins as well as a different operating voltage. So in a way, all four generations of RAMs are not either forward or backward compatible. Suppose you’re having a motherboard supporting DDR3 RAM, and it will not support either DDR2 or DDR4 RAM.
So the DIMM modules available in these form factors are used inside the desktop or a personal computer. But if you see inside the laptop, this DIMM module’s form factor is relatively compact, and it is known as the SO DIMM or Small Outline DIMM modules. So if you see the different generations of SO DIMMs, it has a different number of pins and a different operating voltage.
Similarly, the RAMs used for the graphic cards are known as the Graphic DDR or simply GDDR. Now, as these graphical DDRs are used for multimedia applications. So the amount of data that needs to be handled is relatively more. That is why this type of GDDR RAM has more bandwidth than desktop and laptop memories.
Suppose you find this review helpful and looking for types of DRAM and their generation. In that case, you can select and buy one from the above list suiting your budget, usability, and necessity.
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