In order to give DDR4 a mid life kicker memory vendors are up’ing their game and producing 3DS DDR4 DIMMs.  What is 3DS you ask?  Its 3 Dimensional Stacking of die in a single package.  Not to be confused by ‘twin die’ which is just 2 die next to each other and not stacked.  3DS uses TSV (through silicon via’s) to make the connection between the dies.

3DS is a game changer when it comes to density.  DIMMS of 128GB, 256GB and possibly 512GB on a single DIMM is enabled by this technology.  RDIMMs or LRDIMMs can implement 3DS and have up to 4 ranks.

The 3DS protocol works by introducing the concept of logical ranks in addition to physical ranks.

3DS DDR4 Physical Layout

The screen shot below from the DDR Detective shows what the traffic on a 3DS DDR4 memory bus looks like.

3DS DDR4 waveform

Waveform showing interleaved traffic between the different physical and logical ranks on a single DDR4 3DS DIMM.

The 3DS protocol is also different, as timing parameters between the physical ranks and the logical ranks have to be controlled.  FuturePlus Systems, who took the lead role in JEP 175 DDR4 Protocol Checks, has also created the 3DS protocol checks found in the 3DS option of its FS2800 DDR Detective product.

3DS DDR4 Violations

DDR Detective 3DS specific violations.  These run continuously never missing a clock edge and can run for days checking to make sure no potential for data corruption due to protocol errors occur.

What’s in your Server?  Well if its 3DS you will want to make sure you’re getting your money’s worth as these DIMMs can be $4000 or more for a single DIMM.  BIOS and memory controllers are notorious for causing memory failures only to have the failure blamed on the DIMM.  Don’t be fooled.  If you’re getting memory errors let us find the root cause.  We sell equipment and services that can help.

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