AT cabinets took air in from the front and exhausted it from the PS at the top/rear.
ATX cabinets did the opposite, taking air in from the PS, often cooling the CPU directly, then exhausting it to the front at the bottom.
Which is the superior cooling design? NEXT, take into consideration HDD carriers with the flimsy cooling fans of their own. Do they push against a pressurized cabinet or exhaust from it?