Are DDR2 modules backward compatible?
No. DDR memory sockets can only support DDR. DDR2 and DDR have a different pin count are not interchangeable. To prevent the accidental installation of incompatible memory, DDR2 modules will not fit in a DDR slot due to the shifted DIMM module key/notch back to top • Do DDR2 and DDR modules look different? Yes. The most obvious difference is the pin count. DDR2 has 240 pins and DDR has 184 pins. Additionally, DDR modules are typically built with TSOP (Thin Small Outline Package) style chips, while DDR2 makes use of FBGA (Fine Ball Grid Array) chips which support shorter traces, better signal integrity, and enhanced heat dissipation. FBGA package type chips increase the density of connections by making electrical contact to the PCB with a network of small solder balls located underneath the chip. TSOP chips have visible contact pins on each side of the chip.
