This rig exists to train models, not serve them. Four RTX PRO 6000 Blackwell cards in one chassis at 600 W each is 2.4 kW of heat to evict, and training runs are hours-to-days long with every card pinned at full TDP. Air coolers can do it for an inference burst; they cannot do it for a multi-day training job — the fans get loud, the cards stack their exhaust into each other, and the first one to thermal-throttle stalls the whole synchronous step. So we converted the cards to waterblocks. We did.