I'm working on a project and have been banging my head against the wall for the past couple of weeks with the DDR3 fanout and wiring. I'm trying to keep the cost to the minimum, so I'm using the most cost-effective DDR3 IC's I managed to find, which is 512Mb x16 96-ball packages by Kingston and have four of them connected to an ARM Cortex-A7 CPU. Since I've entirely rerouted the memory subsystem abt a dozen times, trying to fit everything on a 4 layer board with components only on one side (for cost and aesthetic reasons), I decided to check how many layers other people have used for similar projects? As far as I can tell by the laminate of some SBCs I have, others have used at least 6 layers for this. Some seem to go for single chip twin- or quad-die 32x options, but that stretches the production costs by a lot, and I'm trying to keep the costs down.
Has anyone succeeded in routing 2 channels with 2 x16 chips each on a 4-layer PCB, with proper length and skew tuning? I would go for 6-layer PCB, but the price jumps almost twice, and I'm already stretching my wallet with the 4mils(0.1mm) track width and 8mils(0.2mm) via holes. Going to 6 layers, the price hike is significant regardless of the track widths and min drill sizes used.
Any suggestions how to do this better and more efficiently?
Thanks in advance!