In the old days, mainframes were stored on raised platforms in basements, and the largest CPUs were cooled with...
CPUs used a closed, loop system of distilled water that moved warm water from the CPU to a cool-water distribution unit, said SearchWindowsManageability.com reader Jay Lane. Warm water passed along a thick, stainless steel plate, and cool water passed on the other side. The cool water absorbed the heat from the contained, distilled loop of warm water.
Back then most IT departments ran cool water from building air conditioner systems to mainframe cooling units. During Lane's time at the Pentagon, the IT and facility folks decided against this. Instead, they ran a pipe into the nearby Potomac River for the necessary cool water.
The pipe reached the middle of the Potomac and had a series of grates and filters to guard against debris and other contaminates.
One afternoon many years ago at the Pentagon, Lane was working on a terminal attached to a mainframe.
Lane, a programmer, was plugging away on a data file when the terminal screen flashed a message to log off immediately and that the mainframe was going to shut down in five minutes.
"Being a good soldier, I did as ordered and logged off," Lane said.
Like the other users knocked off the network, he rang the help desk. He found out the cooling system's water pressure had dropped so low there wasn't enough water to sufficiently cool the mainframe CPU. The system automatically shut down to prevent the CPU from overheating.
Lane later found out why his workday was abruptly interrupted. A 30-pound fish was sucked into and caught in a grate that filtered water from the Potomac.
The big, unlucky fish greatly reduced the amount of water available to cool mainframe CPUs. The Pentagon mainframes, unaware of anything fishy, automatically shut down.
"Fortunately, the computer was not fined for fishing without a license," Lane cracked, "so the incident was not too costly."