I'm assuming by DDD you're referring to memory. So it's like this:
The PS4 uses 8GB of GDDR5 which is clocked at 2.75GHz with memory bandwidth of 176GB/s.
The Xbone utilizes 8GB of DDR3, but the actual clock speed is 853MHz, which corresponds to their quoted 68.3GB/s memory bandwidth (68.3 divided by
.
Both systems also included a seperate, smaller cache of RAM for small miscellaneous tasks. I didn't see what the PS4's is quoted as being, but the Xbone's is 32MB, which runs faster than the shared DDR3 used for the CPU and GPU functions, but is such a small amount that it doesn't really matter.
It's not clear what the CAS timings are for either console, but it's also largely irrelevant, as both utilize an integrated memory controller, which largely negates those values in the real world.
The GDDR5 used by the PS4 is basically a variant of DDR3 designed for high-bandwidth graphical applications, whereas the DDR3 used by the Xbone is ordinarily only used for system memory, but they're using it for games as well; in a traditional gaming PC, the video card is separate and has its own onboard GDDR that kicks in during games or in apps that can utilize hardware acceleration.
The Xbone also reserves a set amount of its memory pool for the operating system and other non-gaming purposes, making only around 5GB available to developers instead of the full 8GB offered by the PS4. Long story short, it uses dramatically slower memory and allows developers access to only a fraction of what's available.
To put that in perspective, the Wii U uses 2GB of DDR3, and operating systems like Windows 7 x64 require at least 4GB of memory to run properly, which makes the Xbone just a hair above the recommended requirements to run 64-bit apps (and you have to if you want to utilize more than 3GB of RAM) in Windows.