postscript

The numbering goes in the positive direction in x and z. The confusing thing is that there are 2 types of mother boards, 'type 3' and its mirror 'type 4' (these refer to electronic layout and schematics). The correspondence is as follows:

MB number	location	type
MB 1	SE	type 3
MB 2	SW	type 4
MB 3	NE	type 4
MB 4	NW	type 3