Minimum and maximum trace lengths for all signals on the module. Many vendors ignored these requirements when shipping modules constructed on 4 layer boards. Trace width and spacing. Precisely specifies the width of the trace lines on the printed circuit board and the allowed spacing between adjacent traces. Callout for 6 layer boards, including unbroken power and ground planes.
Unbroken planes offer improved power distribution, enhanced signal integrity and lower noise.
Many vendors shipped inferior boards with only 4 layers and broken power and ground planes. Detailed specifications for the distances between each circuit board layer. Such reflections effectively increase signal propagation time, thereby causing signals to be improperly recognized at the end of each clock period. Previous generation DRAM DIMM specifications did not specify detailed layer stackups. Precisely matched clock trace lengths, as well as routing, loading and termination requirements.