Power supplies are not part of the motherboard; they are located in the computer case.
motherboard
+3.3v +5v -5v +12v -12v
What are the 5 voltages produced by and BTX power supply? +12v -12v +5v -5v +3.3v
+12, -12, +5, -5, 3.3 and ground (or 0).
Case form factor determines the physical size of a power supply and the placement of a screw holes. It can be ATX, microATX, BTX and others.
-5v is seldom used because of the ATX12V 1.2 revision in 2003
BTX motherboards use a 24-pin power connector.
+12V, -12V, +5V, -5V, +3.3V -5V is seldom used
+12v,-12v, +5v, ,-5v, +3.3v and the one seldom used is -5v
ATX and BTX are types of motherboards designed by Intel. ATX is the more popular motherboard and has been around since the mid 90's and was designed for the ease of adding and removing components. BTX boards are newer then ATX and were designed to provide better airflow throughout the computer while maintaining the benefits of the ATX design. BTX has improved air flow , can be used in all cases and is able to use ATX power supply.
Power input connector, or just power connector
Power input connector, or just power connector