There are two schools of thought, total isolation of all supplies or make all common to the Earth Ground star point, I have always followed the latter on P.C. bases systems.
It is usually not the P.S. that is grounded, but the M.B. ground plane.
Older P.C.s often had nylon stand offs for the M.B. but modern design is usually 6 or 7 ground plane screws that mount to the earth grounded frame of the P.C cabinet.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.