I.MX6 Dual/Quad: how many sticks of DDR3 SDRAM can it take? - Page 1
Forum section: electronics / general

author: technix
author_rank: Super Contributor
timestamp: February 13, 2019, 05:18:43 am
content: That series of chips claims that it supports SODIMM and regular DIMM memory modules, using its full 64-bit memory bus interface. It has two sets of CS and CLKp/n lines. The Micron DDR3L module datasheet suggests that the memory stick takes one set of CS and CLKp/n signals. suggesting the chip supporting two DDR3 memory sticks.Questions:1. Do that chip actually support 2 sticks of DDR3 DIMM? Or did I read the Micron DDR3L datasheet wrong?2. The chip has address lines up to A15 and suggests a supported row and column address width matching that of Micron’s 4GB sticks. Do this suggest that the chip supports a single 4GB DIMM stick?3. If my boards use DIMM sticks, is there any examples of memory initialization code that uses the SPD data? I don’t need XMP as that chip does not support anything faster than DDR3-1066.4. When auto-configuring the memory using SPD data, how to configure the memory controller to skip one of the two memory sticks in case that the two memory sticks don’t match? Can I skip CS0 while keeping CS1?5. What storage media should I use to put the SPD-capable boot loader? The boot loader is going to be fairly large as it contains multitude of drivers. (I support booting over PCIe NVMe for example.)

author: dgtl
author_rank: Regular Contributor
timestamp: February 13, 2019, 12:19:18 pm
content: Afaik, NXP officially does not support socketed RAMs. Their approach is to calibrate each design once using a tool they provice and then use hard-coded calibration constants. But Novena project did use socketed RAM, probably they got it working somehow. Perhaps start at looking Novena-specific open-source stuff?

author: technix
author_rank: Super Contributor
timestamp: February 13, 2019, 02:31:36 pm
content: Quote from: dgtl on February 13, 2019, 12:19:18 pmI hope it is possible to run the calibration during every boot. Also from a passing mention on the manual NXP did claim that the chip supports DDR3 SODIMM.My ideal form factor for that board is a 17cm square board conforming to mini-ITX form factor and uses standard ATX power supply. Instead of the FPGA my board would contain a PCIe bridge chip that breaks the single PCIe root complex into several lanes (think south bridge in PC) to serve an standard PCIe slot and a combined NVMe/SATA M.2 slot.

author: NorthGuy
author_rank: Super Contributor
timestamp: February 13, 2019, 02:48:04 pm
content: It is not about number of sticks, but about number of ranks. SODIMM may have 2 ranks (each rank has its own Sx# pin), which is the same as if you had 2 single-rank SODIMMs (except for SPD, of course). Regular DIMM may have 4 ranks. So, if your chip only supports 2 ranks, there's no need to install two sockets. One SODIMM will do just as well.

author: nctnico
author_rank: Super Contributor
timestamp: February 13, 2019, 03:44:11 pm
content: Quote from: technix on February 13, 2019, 02:31:36 pmIIRC the iMX5 does a calibration at startup and I expect the iMX6 will do the same.

author: technix
author_rank: Super Contributor
timestamp: February 14, 2019, 03:21:15 am
content: Quote from: NorthGuy on February 13, 2019, 02:48:04 pmSo you are suggesting that I got the datasheet wrong? Do you have a datasheet for a dual-rank and a quad-rank DIMM, and a dual-rank SODIMM? (Is there even any quad-rank non-ECC DDR3 UDIMM at all?)

author: NorthGuy
author_rank: Super Contributor
timestamp: February 14, 2019, 05:27:13 am
content: Quote from: technix on February 14, 2019, 03:21:15 amIt is often hard to find datasheets for DIMM modules. Typically if you see chips on both sides, it's dual rank. Micron has datasheets for their dual rank SODIMMs such as EBJ81UG8EFU0, MT16KTF2G64HZ. JEDEC document is Standard 21C 4.20.18 - "204-Pin DDR3 SDRAM Unbuffered SO-DIMM Design Specification", although I believe they now want money for their standards.I've never worked with (non-SO) DIMMs (besides installing them in my computer). There are lots of quad-rank DIMMs for sure. I don't think they're necessarily ECC, but I may be mistaken. ECC DIMMs are basically the same thing as non-ECC, except there are 72 lines instead of 64.

author: technix
author_rank: Super Contributor
timestamp: February 16, 2019, 09:18:48 am
content: Quote from: NorthGuy on February 14, 2019, 05:27:13 amI didn't find anyone actually making 4-rank DDR3 non-ECC UDIMM at all on JEDEC website...Maybe I can just use a single stick of regular DIMM on that chip? Or can I wire up two RAM slots in a way allowing for dual-rank RAM module in slot 1 or two identical single-rank RAM modules in the two slots?

author: NorthGuy
author_rank: Super Contributor
timestamp: February 16, 2019, 03:21:04 pm
content: Quote from: technix on February 16, 2019, 09:18:48 amIf your chip only supports 2 ranks, why do you need a 4-rank module?Quote from: technix on February 16, 2019, 09:18:48 amYou certainly can do this. If you go with SODIMMs, there are special connectors which let you install 2 SODIMMs one over the other. The bottom connector holds SODIMM at 5 mm above the PCB. The top connector solders next to it and holds SODIMM at 9 mm above the PCB.

author: technix
author_rank: Super Contributor
timestamp: February 17, 2019, 02:35:34 am
content: Quote from: NorthGuy on February 16, 2019, 03:21:04 pmI just want to prove a point that for DDR3 non-ECC UDIMM the 4-rank capability of a full-size DIMM slot is unused.Quote from: NorthGuy on February 16, 2019, 03:21:04 pmI am using full-size DIMMs.

author: NorthGuy
author_rank: Super Contributor
timestamp: February 17, 2019, 03:04:27 pm
content: Quote from: technix on February 17, 2019, 02:35:34 amThis may be difficult to do. The market is huge. If you cannot find something doesn't mean it doesn't exist (or existed in the past).

author: technix
author_rank: Super Contributor
timestamp: February 17, 2019, 05:47:02 pm
content: Quote from: NorthGuy on February 17, 2019, 03:04:27 pmI scraped the JEDEC registry for any mention of a 4-rank non-ECC DDR3 UDIMM SDRAM module, but there is none of them. non-ECC UDIMM doesn't even have 16GB and 32GB options, let alone for me I am restricted to 4GB anyway.