Butterfly Backplanes
Some backplanes are constructed with slots on both sides. These are not the same as midplane backplanes. A butterfly backplane is typically constructed to maximize the number of slots for the least vertical height. The backplane would be mounted vertically in a chassis oriented front to back and the plug-in SBC and cards would lay flat, protruding out both sides of the backplane. This, for example, allows the use of up to four full height boards in a 2U chassis.
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