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C29x 32bit DDR3 to 64bit SO-DIMM socket?

Question asked by Ondrej Ille on Sep 7, 2016
Latest reply on Feb 13, 2017 by Ondrej Ille

Hi,

I am creating an PCIe board with C291 CPU with Hardware accelerated encryption. This CPU has 32 bit DDR3 controller. I would like to route the DDR to the standard SO-DIMM socket, because it is less prone to errors. Also when the device operates in the PKCAL mode it does not use the DDR at all, so the memory is not needed. It is more flexible to have the SO-DIMM than have two assembly version (one with memories soldered on PCB, the other one without).

 

The question is: Is it possible to route the 32 bit DDR controller(of C291) to the SO-DIMM 204 pin socket? This socket has 64 bit wide DDR interface. In theory it should be possible that just half of data signals and strobes are connected and the rest remains unused (data 32-64). Thus only half of the chips on board in socket would be used (I dont mind this). It is better to get big,cheap memory to DIMM socket and use only its 50% than have custom,hardwired chips on board. If it is possible how should I treat the Data 32-64 pins of the SO-DIMM socket??

 

The other option would be to have 144-pin 32 bit DDR3 dim memory. This is not acceptable since it is not used and i did find nearly no memories like this available...

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