DDR3 made its debut in mid-2007 when Intel released P35 chipset with support for DDR3. Today nearly all desktop, mobile and server platforms support DDR3. iSuppli estimates that DDR3 will account for roughly 90% of DRAM sales this year. However, the next generation DRAM technology is already just around the corner and JEDEC is scheduled to release the full DDR4 specification next year. Yesterday, JEDEC published some of the specifications of the upcoming DDR4 technology. 

First and foremost, DDR4 will concentrate on performance and power consumption. The latter is achieved by lowering the voltage to 1.2V, compared to DDR3's 1.5V (although there are DDR3 modules with lower or higher voltage but 1.5V is the standard for most). The performance gain is achieved by increasing the frequency and DDR4 will start from 1600MHz. It's likely that we will see 1866MHz or 2133MHz modules as the standard though, considering that DDR3 went straight for 1066MHz as well, even though a 800MHz specification existed too. The projected maximum speed for DDR4 is 3200MHz but then again, DDR3's maximum is 1600MHz, yet 2133MHz DDR3 modules are available. We will likely see even higher bandwidth DDR4 modules in the future. JEDEC lists the prefetch buffer for DDR4 as 8n, which is identical to DDR3. If this ends up being the case the bulk of the performance increase will be due to higher operating frequencies enabled through more advanced signaling.

The higher operating frequencies come at the expense of some serialization of the interface. The SDRAM memory interface remains one of the last parallel buses in modern PCs. While it doesn't look like DDR4 will change that, we have heard reports of the new memory standard moving to a point-to-point protocol. In other words: one DDR4 module per memory channel. Note that JEDEC hasn't confirmed this will officially make it into the DDR4 spec.