I'm trying to get a feel for what it looked like when you designed a computer to have a lot of memory chips stuffed into it. To that end, I found this: https://commons.wikimedia.org/wiki/File:VAX_11_780_16mb_memory_board.jpg
If I'm counting correctly, that's 256 RAM chips on the visible side of the board. Assuming the use of 256kbit RAM chips, 256 x 256 x 1024 / 8 = 8Mbytes on the visible side, so if it's double-sided, that would be correct.
What are the physical dimensions of the board? Height, width, and depth in terms of how far apart they are spaced in the machine?
