Ok, so time to pick some RAM. The reference manual mentions both LPDDR2, DDR3 and DDR3L. The L in DDR3L stands for Low Voltage, which makes sense. There's apparently a few modes - DDR3 x16 - DDR3 x32 - DDR3 x64 - LPDDR2 2-channels x16 - LPDDR2 2-channels x32 Let's see what Archer did and what the reference designs do. - Archer is [MT41K256M16HA](https://www.digikey.ca/en/products/detail/micron-technology-inc/MT41K256M16HA-125-E/4251401) DDR3L 4Gbit x2 - iMX Rex is [MT41J128M16HA](https://www.digikey.ca/en/products/detail/micron-technology-inc/MT41J128M16HA-15E-IT-D/2663613) DDR3 2Gbit x4 - Colibri uses DDR3 64bit - imx6SLL used MT52L512M32D2PU-107 WT:B - wandboard uses H5TQ2G63BFR-pb DDR32 2Gbit x 4 Question: What's the difference between 256M x 8 and 128 x 16? It seems usually the schematics use x16, maybe since 2 of them together is 32 and that's a full address? > The chip can handle up to 4 Gbytes of DRAM memory It seems like the OpenRex / imx6 rex use 4x memory chips with "up to 4GB", implying each chip is 1GB. Are smaller variants using 4 chips with less capacity or less chips? The above was wrong. Each chip is 4 Gigabits! so 16 Gigabits / 8 = 2 Gigabytes. The main chip is [MT41K256M16TW-107:P](https://www.digikey.ca/en/products/detail/micron-technology-inc/MT41K256M16TW-107-P/5956623) which has replaced the older chip. That the imx rex uses. $4.11 x 4 is not too bad for a total There was a larger capacity part: www.digikey.ca/en/products/detail/micron-technology-inc/MT41K512M16HA-125-IT:A/5956635 or this one: https://www.digikey.ca/en/products/detail/alliance-memory-inc/MT41K512M16HA-125-ATR/15766059 but it's $40 per chip! Although I was reading [So You Want To Build An Embedded Linux System](https://jaycarlson.net/embedded-linux/) and he mentions picking 1 chip of RAM to avoid complex routing issues, which has me reconsidering the larger capacity part. Some useful forum discussions: - [i.MX6 4GB Memory (2 chips)](https://fedevel.com/forum/your-projects/5710-i-mx6-4gb-memory-2-chips) After some thinking, I should optimize for the simplest thing that works at first, even if it's pricier. So we're going with the [MT41K512M16VRP](https://www.digikey.ca/en/products/detail/micron-technology-inc/MT41K512M16VRP-107-AAT-P-TR/17631337) . There's a few variations that I think have to do with if they are "automotive" grade or not, but I don't think I care. It's pricey at $28 a chip. It's slower because we'll only have x16 data pins. But it's a single part to route with no weird matching. And we'll find out how slow it is. The [datasheet](https://cdn.tahnok.ca/u/DDR3L_8Gb_x16_1CS_TwinDie_V00H-1840279.pdf) was a bit annoying to find, since digkey links to a 404, but mouser had mirrored it, so I've mirrored it too.