DDR2 (Double Data Rate 2) and DDR3 (Double Data Rate 3) are both types of RAM (Random Access Memory), but they have key differences in speed, performance, and physical appearance. Here's a breakdown:
Speed
DDR2 Actual image
DDR3 Actual image
DDR2:
- Data Transfer Rate: Typically ranges from 400 MHz to 800 MHz.
- Bandwidth: Up to 6.4 GB/s (for DDR2-800).
- Latency: Generally higher compared to DDR3.
DDR3:
- Data Transfer Rate: Typically ranges from 800 MHz to 2133 MHz.
- Bandwidth: Up to 17 GB/s (for DDR3-2133).
- Latency: Generally lower compared to DDR2, meaning better overall performance.
Physical Appearance
DDR2:
- Pin Count: 240 pins for DIMMs (Dual In-line Memory Modules).
- Keying: The notch (key) on the DDR2 module is positioned slightly off-center and is different from DDR3, to prevent improper insertion into the wrong slot.
- Height and Layout: DDR2 modules are slightly taller and have a different layout compared to DDR3.
DDR3:
- Pin Count: 240 pins for DIMMs, but the arrangement and keying are different.
- Keying: The notch on the DDR3 module is located in a different position than that on DDR2, which ensures compatibility with DDR3 motherboards and prevents inserting DDR3 into DDR2 slots.
- Height and Layout: DDR3 modules are generally shorter and have a different heat spreader design.
Summary
- Speed: DDR3 offers higher speeds and better bandwidth compared to DDR2.
- Physical Appearance: DDR3 modules have a different notch position compared to DDR2 and are generally lower in height. This physical difference helps prevent compatibility issues between DDR2 and DDR3 slots.
If you're upgrading or building a system, make sure your motherboard supports the specific type of RAM you're planning to use, as DDR2 and DDR3 are not interchangeable.