Difference between DDR and DDR2

1. DDR : DDR stands for Double Data Rate. It is used in computers and laptops, and it can transfer double data chunks to memory per clock cycle, that's why it is called double data rate. Since the launch of DDR RAM, there have been many upgrades, which are called DDR2, DDR3, DDR4. All new versions of DDR RAM are not compatible with the earlier or later RAM. This means that the DDR2, DDR3, DDR4 memory module will not be compatible or fit in any slot in the DDR or DDR1 slot of the motherboard. 2. DDR2 : DDR2 stands for Double Data Rate version 2 It is the second version of DDR memory. This version of RAM was developed to achieve a high data rate for block-transferring. It is the successor to DDR where the main change is applied to the operational frequency between the RAM chip and the prefetch buffer, and the amount of both parameters is increased. The prefetch buffer is 4-bit memory catch that resides in the DDR2's RAM chip.
Difference between DDR and DDR2 :

S.No.	DDR	DDR2
1.	DDR has 4 internal banks.	Whereas DDR2 has either 4 or 8 internal banks.
2.	The transfer speed of the DDR varies between 0.20–0.40 gigatransfer per second.	While the transfer speed of DDR2 varies between 0.40–1.06 gigatransfer per second.
3.	The speed of DDR is slower than that of DDR2.	While the speed of DDR2 is higher than DDR.
4.	The DDR was released in the year 1998.	While DDR2 was released in the year 2003.
5.	DDR is succeeded by DDR2.	While DDR2 is succeeded by DDR3.
6.	The standard supply voltage of DDR is 2.5 V.	While the standard supply voltage of DDR2 is 1.8 V.
7.	DDR has a bus clock speed of 100 MHz-200 MHz.	While DDR2 has a bus clock speed of 200 MHz-533 MHz.
8.	DDR has a channel bandwidth of 1.60-3.20 GBps.	While DDR2 has a channel bandwidth of 3.20-8.50 GBps.
9.	Performance wise DDR is not better than DDR2.	Whereas it is better than DDR in terms of performance.