DDR2 and DDR3: The Differences

As computer technology has advanced, so too have the types of memory they use. One of the newer, faster versions of memory developed is DDR (Double Data Rate) memory. The main concept behind DDR memory is that, by applying a row address to the chip, a larger number of bits are accessible at the same time within the chip. There are two common types of DDR memory: DDR2 and DDR3. In this blog, we will discuss both types and the main differences between the two.

DDR2 was the second version of DDR memory. This version of RAM was developed to achieve a high data rate for block-transferring. DDR2 can transfer data at the clock rate of 400 to 1066 MHz. As stated, DDR2 was the successor to DDR. The main changes were in the operating frequency of the RAM chip & prefetch buffer and the increased quantity of both the parameters. A prefetch buffer is a 4-bit memory cache located in the RAM chip of DDR2. It is used in the RAM chip to preposition the bit in the data bus as quickly as possible. DDR2 is a 240 pin DIMM (Dual In-line Memory Module) architecture that operates at 1.8 volts. These DIMMs are composed of one or more RAM chips in a single board connected to the motherboard. The voltage of the DDR2 is reduced from DDR technology to reduce the heat effect.

DDR3 is an advanced version of DDR2. It has an increased prefetch buffer of 8 bits and increased operating frequency of 1600 MHz. The amount of voltage power in DDR3 is 1.5 volts, further decreasing the heating effect. Similar to DDR2, the pin architecture of DDR3 features 240 pins, but these cannot be used in the motherboard RAM of DDR2 due to differing notched keys. DDR3 also has the unique option of clearing the memory by software reset action. This memory reset option ensures that the memory is cleared and emptied after each system reboot.

To review, there are seven key differences when comparing DDR2 and DDR3 directly. First, DDR2 memories work within the range of 400 to 800 MHz and generate data rates up to 800 Mbps. Adversely, DDR3 works within the range of 800 to 1600 MHz and produces data transfer rates up to 1600 Mbps. Second, DDR2 consumes more power, as its supplied voltage is 1.8 volts. The supplied voltage of DDR3 is 1.5 volts, significantly reducing the heating effect caused by high frequencies. The third difference is in the two memory’s bit sizes. DDR2 has a 4-bit buffer while DDR3 has an 8-bit buffer.

Fourth, DDR2 does not offer any reset options, while DDR3 does. Additionally, DDR3 is significantly faster than DDR2. The sixth difference is the latency of the two memory types. DDR2 has a lower latency than DDR3. This is important because lower latency provides better performance. The final difference is the cost; DDR3 memory is more expensive than DDR2. In conclusion, DDR2 is the earlier version and now somewhat outdated. DDR3 is a newer technology and provides added features such as increased storage space, low power consumption, faster clock speed, and greater system flexibility.

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