Difference Between DDR,DDR2 and DDR3 RAM

Characteristics	DDR1	DDR2	DDR3
Bus Clock(MHz)	100-200	200-533	400-1066
Internal Rate(MHz)	100-200	100-266	100-266
Prefetch (Min. Fetch)	2n	4n	8n
Operating Voltage	2.5/2.6	1.8	1.5
DIMM Pins	184	240	240
SO-DIMM Pins	200	200	204
Micro DIMM Pins	172	214	214
Transfer Rate(MT/s)	200–400	400–1066	800–2133