Xbox One features 8GB of DDR3 RAM, a slower type of memory to PS4's GDDR5, online reports have confirmed.
Joystiq has published a report of the upcoming console's specs, which is said to include an "8 Core CPU custom built by Microsoft" and the DDR3 memory. IGN also says that the console's RAM is confirmed to be DDR3-spec.
Though DDR3 memory is widely used in electronic devices, GDDR5 is designed specifically for high bandwidth video use.
3GB of Xbox One's RAM is also said to be reserved for system resources, including apps and the console's three operating systems, leaving 5GB for other processes.
Sony, on the other hand, is said to have "already ring-fenced the system memory away from the game memory," suggesting that PS4 developers may have access to the full 8GB for game development.
Source: Joystiq, IGN