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KingVita89 , 04-02-2017, 07:21 AM

Hi,

I would like to know if it is possibly to use two Chips of DDR3 each 2 GB to get total 4 GB with i.MX6 Dual or Quad?

@Robert I saw in your iMX6 Rex board that you use four 2 GB DDR3 RAM chips to get total 4 GB. But Why?

I hope someone can give some explanation on this topic.

Thanks!

robertferanec , 04-03-2017, 11:44 AM

I have not seen any 2GB one die DDR3 memory chips which could be used to create 4GB if you use two of them in the Rex design. Do you have any specific memory chips in mind?

Are you sure? This is maybe a mistake and you thought something else?

KingVita89 , 04-03-2017, 12:19 PM

Maybe one of them https://www.micron.com/products/dram/ddr3-sdram ?

In the BOM of iMX6 Rex there is a DDR3 SDRAM 2GBIT 667MHZ 96BGA listet 4 times.

Could you please have a look? Did I missed something?

By the way is iMX6 ,,only'' capable of max 4 GB RAM?

robertferanec , 04-03-2017, 01:38 PM

Do not get confused with Gbits(Gb) and GBytes (GB). If memory size is in Gb (Giga bits), you need to divide the memory chip capacity by 8 to get GB (Giga Bytes) ... and then multiply it by number of chips to get board memory size.

KingVita89 , 04-07-2017, 09:10 AM

Thanks for clearing up understanding memory density. I wonder if I can use for i.MX 6 one or two chip solution to get max supported 4GB memory e.g. https://www.micron.com/products/dram...%5D=Production. My goal is to save space on PCB price is secondary.

Are there other limitation for depth or width?

In Rex Modul there are 4 DDR3 module to get 1GB I think to save cost or are there other reasons to go with 4 chips instead of 1 or 2?

mairomaster , 04-07-2017, 09:35 AM

The link you've given as an example has LPDDR3 memory, I am not sure if i.MX6 supports that type. I know it supports LPDDR2 (I've done such design), but using mobile memory is not as trivial as using standard DDR3 due to different reasons.

Doing a quick search on Micron's website, I found some 16 Gbit DDR3 and LPDDR2 options:




I am not sure if those will surely work with i.MX6 though, didn't have much time to look in detail. Choosing RAM requires a serious research.

KingVita89 , 04-07-2017, 09:59 AM

You are right i.MX6 supports 2x32 LP-DDR2 or 1x64 DDR3 / LV-DDR3 memory. Could you please short explain why mobile memory is harder to implement (other Layout rules /topology)?

Could you please give an example of one memory IC which you use for your LPDDR2 design that surely works with i.MX6?

robertferanec , 04-07-2017, 03:45 PM

- 4 chips uses 64bit data bus, 2 chips only use 32bit data bus - that is half of the through put.
- Low Power DDR3 (LPDDR3), usually this means, that memory chips and memory controller is running on lower voltage and it may not be supported by all the chips.
- I could not download the datasheet, but for mobile memories double check the footprint, chip physical size and ball pitch. Some require advanced PCB technologies

mairomaster , 04-12-2017, 10:12 AM

One memory that I know works for sure with iMX6 Dual Lite is Micron MT42L128M32D1GU-25 WT (in two chip configuration).

MadhuWesly , 04-14-2017, 07:46 AM

Hi,
I would like to get clarified on few doubts related to DDR3L( a Low voltage(1.35V) version of DDR3) interface with iMX6 Quad SoC, could you please clarify...

1. Will it be OK if we use only 32-bit data interface in the SoC instead of using all the 64-bit data interface? Will it be OK if I leave the unused data pins on the SoC unconnected?
2. How to initialize the DDR3L RAM chip initially? I came to know that the calibration sequence has to be executed after the DDR memory has been initialized. Am I correct? It would be helpful if there is any documentation.

robertferanec , 04-14-2017, 11:11 AM

1. I would try to configure the memory controller for 32-bit operation on a standard 64 bit board and see if everything is working oki. Then I would probably build a board with 2 memories fitted (but be aware your layout may need to be done the way that it creates minimum stubs if you unfit two memories). We use the same PCB for SOLO (32bit) and QUAD (64bit) - works oki.

2. I have never tried DDR3L on iMX6, but maybe the configuration is the same? I would probably just search NXP document with register description for DDR3L and see if there are specific settings for it.

Possibly try to ask at freescale/nxp forum. The may be able to help.