What is the Difference Between DDR2 and DDR3?

The main differences between DDR2 and DDR3 memory modules are as follows:

1. Prefetch Buffer Width: DDR3's prefetch buffer width is 8 bits, while DDR2's is 4 bits.
2. Speed: DDR3 has a higher clock speed and data transfer rate compared to DDR2. DDR3's clock speed ranges from 1066 to 1600 MT/s, while DDR2's clock speed ranges from 533 to 800 MT/s.
3. Power Consumption: DDR3 consumes less power than DDR2, with DDR3's voltage being 1.5V compared to DDR2's 1.8V.
4. Voltage: DDR3's operating voltage is 1.5V, while DDR2's is 1.8V.
5. SDRAM Functions: DDR3 introduces two functions, Automatic Self-Refresh (ASR) and Self-Refresh Temperature (SRT), which allow the memory to control the refresh rate according to temperature variations.

In terms of physical appearance, DDR2 and DDR3 RAM modules look largely similar, with the same length and number of pins (240). However, the notch positions differ, with DDR2's notch located near the middle of the RAM stick and DDR3's notch positioned nearer to the end. This difference prevents intercompatibility between the two types of RAM modules, meaning DDR2 RAM can only be used in DDR2 slots and DDR3 RAM can only be used in DDR3 slots.

Comparative Table: DDR2 vs DDR3

Here is a table comparing the differences between DDR2 and DDR3 RAM:

DDR2 and DDR3 RAM have similar physical appearances, but DDR3 offers better performance while consuming less power. The main differences between DDR2 and DDR3 RAM include the clock speed, maximum transfer rate, voltage, prefetch buffer width, and data rate.