In an article on Embedded.com (a sister site), Syed W. Ali, an advanced certified designer and layout engineer for Nexlogic Technologies, looks at the challenges and best ways forward when migrating an embedded PCB design from DDR3 SDRAM to DDR4. Here’s an excerpt.
PCB and embedded systems designers are scratching their heads these days, facing some uncertainty as they start mapping out the move from DDR3 SDRAM to DDR4. Routing DDR2 signals on a PCB was tough enough. But with DDR3 it proved to be even more difficult and challenging. The big question now is: will DDR4 be just as much of a challenge? More? Or less?
Double data rate synchronous dynamic random-access memory (DDR SDRAM) is the most commonly used class of memory integrated circuits used in today's microprocessor-based systems. DDR SDRAM, also called DDR1 SDRAM, over the years was superseded by DDR2 SDRAM and DDR3 SDRAM, neither of which is backward compatible with DDR1 SDRAM. As a result, DDR2 or DDR3 memory modules will not work in DDR1-equipped printed circuit boards. The trend continues with DDR4 and it is up to PCB designers to make it work.
To make the transition from earlier DDRAM versions to DDR4, it is important to review the main differences between DDR2 and DDR3 and find out what can be learned that will be useful transitioning printed circuit board designs to DDR4.
Read the entire article on Embedded.com, where Ali discusses the similarities and differences of the two memory modules, their impact on PCB design, and routing considerations.
Thank you fir sharing the information about the privisions to be made on the PCB for an easy migration from DDR3 to DDR4 or the vice versa. But as the DDR4 works on 1.2V where as DDR3 works with 1.7V, the backward compatibity issue would still remain from power supply point of view.