DDR Design using PCIe(Slotted one)

[Lakshmi]

Hi,
I'm doing a project where Processor(RK3399) supports 2 channels of 32bit. I have chosen DDR3 16 bit 8Gb (512M x 16) and my idea was to use 2 these DDR3 and Have 2GB.

https://www.digikey.in/product-detail/en/alliance-memory-inc/AS4C512M16D3L-12BCN/1450-1271-ND/5298017

So my senior told me to use one DDR and another as a slotted one which comes in the computers(I believe it as PCIe interface). The processor has 2 PCIe interface
Can anyone have an idea of how to do OR any reference layout/Guidelines?

[Paul van Avesaath]

there are a few Micron app notes on designs like this.. and I believe I have seen a few Samsung / Philips(nxp) reference designs with the computer based formfactor designs (ram banks).. but both module and direct chip have kind of hte same specification... you still have to match the signals..

https://www.google.com/search?q=micr...hrome&ie=UTF-8

if it really is PCIe interface then there should be reference design on how to do it. because it most likely has a controller on board.. so you need to know what interfaces it supports. meaning extra signals to get the module to work..

good luck

[Lakshmi]

No sorry Question was mistaken.
I RK3399 Processor in which I'll be using One DDR3 Chip another using slotted Connector like these:

https://www.te.com/usa-en/products/connectors/card-socket-connectors/memory-sockets.html

OR

https://www.howtogeek.com/174482/what-does-the-ram-slot-color-coding-on-motherboards-mean/

I thought it was using PCie Interface But it's not.
This connector will routed to Memory controller of Processor.

[Lakshmi]

Any design guidelines for the above?

[Paul van Avesaath]

well i thought so, but you will have to do actually the same things as for a onboard chip. (routing / timing) but you have to make sure that there ar not any other items that need to be connected. (liker power supply and stuff)

after one google search i found

http://opensource.rock-chips.com/images/d/d1/RK3399_Design_Guide_V1.0_20170420.pdf

http://opensource.rock-chips.com/images/6/60/Rockchip_RK3399_Datasheet_V1.6-20170301.pdf

if you google around a bit you will find a few things that might help i would suspect.

but also look at other manufacturers

https://www.nxp.com/docs/en/application-note/AN2582.pdf

search for DIMM bank Layout or something similar

also contact the manufacturer of the DDR3 Membank or your RK3399 supplier to ask for help..

goodluck

[Lakshmi]

Yea sure thanks for the first link. Will help a lot lot to me.
Thanks again.

[robertferanec]

Have you seen a RK3399 board with soldered down on board memory + SO DIMM slot? Or have you seen any RK3399 board with SO DIMM slot? Here is a search:
https://www.google.com/search?q=RK33...ih=920#imgrc=_

If this kind of boards exist, then go for it. If they do not exists, it may be a risk to go this way - some chips do not have good enough buffers or they simply do not support SO-DIMM slots (or, they have never tested it if it works). Do not forget, you need to understand what you are doing, you may need to add software support for it (you need to read SPD parameters and set memory controller based on it), you need to know how to place and how to route these chips and slot (ideally find a design with on board memories + slot and have a look how they routed it). Also, when you finish layout, you may want to simulate it.

Do not forget. If it doesn't work, your whole board will not work and you will need to redesign the memory layout.