Silicon vias in sub-40nm 32Gbyte DDR3 from Samsung

Samsung has used through-silicon vias (TSVs) and 3D packaging to cut power in 32Gbyte DDR3 registered DIMMs (RDIMMs) for servers.

"TSV allows us to stack dies onto one another and therefore increase the density of any given package," Samsung spokeswoman Ujeong Jahnke told Electronics Weekly. "The RDIMM is manufactured by stacking 4Gbit DRAM die."

The module consumes 4.5W, claims Samsung: "Compared to the 30nm-class [sub-40nm] 32Gbyte load-reduced DIMM [LRDIMM], which offers advantages in constructing 32Gbyte or higher memory solutions, the 32Gbyte RDIMM module provides approximately 30% energy savings."

RDIMM is used in high-end servers.

"The 'register' helps to maintain and improve signal integrity," said Jahnke. "'LRDIMM is a variation of this which helps to reduce the loading the modules puts on the memory channel and therefore improves the system speed."

All activities to improve signal integrity typically have trade offs.

According to Jahnke, A simple ECC DIMM in one module/channel configuration will out-perform a RDIMM in one module/channel configuration, but in a three DIMM/channel configuration, the RDIMM will be faster.

Similar, a LRDIMM will help where there are many modules or ranks on a single channel but the best solution will be to reduce the number of DRAM chips on the channel by increasing the density of each chip.

"This is where the TSV technology comes in," she said.

The new RDIMM can transmit at up to 1,333Mbit/s, compared with 800Mbit/s of preceding quad-rank 32Gbyte RDIMMs, claimed the firm.

Engineering samples have been released for evaluation.