Conventionally used in mass-produced "name brand" retail systems, the LPX
motherboard form factor goes into the small Slimline or "low profile" cases typically
found on these sorts of desktop systems. The primary design goal behind the LPX form
factor is reducing space usage (and cost). This can be seen in its most distinguishing
feature: the riser card that is used to hold expansion slots.
Instead of having the expansion cards go into system bus slots on the
motherboard, like on the AT or ATX motherboards, LPX form factor motherboards put
the system bus on a riser card that plugs into the motherboard. Then, the expansion
cards plug into the riser card; usually, a maximum of just three. This means that the
expansion cards are parallel to the plane of the motherboard. This allows the height of
the case to be greatly reduced, since the height of the expansion cards is the main
reason full-sized desktop cases are as tall as they are. The problem is that you are
limited to only two or three expansion slots!
LPX form factor motherboards also often come with video display adapter cards
built into the motherboard. If the card built in is of good quality, this can save the
manufacturer money and provide the user with a good quality display.