September 14, 2010 -- The transition to newer DRAM technologies and densities is increasing. Specific DRAM types such as SDRAM 512Mbit, DDR1 1Gbit, and DDR2 2Gbit are EOL'd (end-of lifed) by DRAM suppliers long before the end applications stop shipping. Initially, two or three DRAM suppliers manufacture these types of DRAMs, but they drop off and shift their resources to the next newest technology. The initial outlook in designing in these DRAMs is promising, but over a shorter time than expected, they get phased out, leaving OEMs with only one supplier which can be very costly or forced into a printed-circuit board (PCB) redesign. While these products may still be profitable for DRAM manufacturers, they don't justify the allocation of newer processing equipment.

One way to address these challenges is to use the long-established industry solution of DRAM stacking. DRAM stacking leverages readily-available, longer-life DRAMs into higher density and/or specially configured stacks. DRAM stacking consists of using two off-the-shelf, 100% tested BGA or TSOP DRAMs. For BGA DRAMs, a PCB cavity is used to stack the DRAMs together and route the signals from one DRAM to another.

By Arthur Sainio. (Sainio is with SMART Modular Technologies)