Hi, y'all. I wound up making my own "clone" of Andy's Mega 2560 SRAM expansion, which uses a full-width connector across the end of the board, picking up power and ground. I also moved the jumpers for the LEDs a bit. And let Eagle do most of the routing.
I wound up doing 4 layers mainly because I could. The board is on Osh Park at https://www.oshpark.com/shared_projects/5dhn3IBO
Board and schematic are on github: https://github.com/telanoc/mega2560_xmem
I've got one put together (jeez, I didn't realize how small those chips were) and it's working with no issues.
Hi Pete, your board looks great. 4 layers huh? If you've got a continuous ground plane below the top then your signal integrity should certainly benefit from that.
Yes, I have one plane for VCC and one for ground (besides top and bottom).
Here's a pic of board #3, still needing a bit of flux cleanup. I've been running the xmem::selftest() in a loop for 15 minutes or so.
By the way, a big "Thanks" for designing this thing in the first place.