In general, assembling the PASTA node is quite simple. For "small" modules, (those with a single 60-pin connector), the modules may be assembled into a stack in any order by simply mating the 60-pin connectors.
For "large" modules, (those with a 180-pin connector grouped into three sections of 60-pins each), some care must be taken to establish the proper order of the stack. The requirement is that some modules must be placed in the stack "above" the processor module, while other modules must be placed "below" the processor modules.
One side of the processor module is designated as the "top" side. This is the side with the low-profile components, (including the processor itself). The top side also has the socket half of the 180-pin connector.
The opposite side of the processor module is designated as the "bottom" side. This side has the taller components, (such as the tall shielded crystal), as well as the LEDS. The bottom side has the header half of the 180-pin connector.
Whenever this manual refers to the orientation of the processor board, the terms "top" and "bottom" are used as defined above. This convention is unrelated to the physical orientation of the node itself, (eg. the node might be packaged such that the "bottom" side is closer to the top of the box than the "top" side).
A similar convention is used to describe modules that are placed "above" or "below" the processor module in the stack.