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Computers That Can't Fail

When you see reports about the small, remote-controlled drones that the military uses to gather intelligence and target enemies in Pakistan and Afghanistan, it’s easy to assume that all our weaponry is equally modern. Some significant weapons systems that our military depends on today, though, run on technology that dates back, in some instances, to the Vietnam War era.

The U.S. Navy’s ship-based radar systems and Britain’s Atomic Weapons Establishment, which maintains that country’s nuclear warheads, use PDP minicomputers manufactured in the 1970s by Digital Equipment Corporation (DEC). Another user of the PDP is Airbus, the French jetliner manufacturer.

The PDP was among the second wave of mainframes called minicomputers because they were only the size of a couple of refrigerators instead of big enough to fill a room.

The F-15 and F-18 fighters, the Hawk missile systems, parts of the U.S. Navy submarine fleet, and Navy fighter test systems on aircraft carriers use DEC’s VAX minicomputers from the 1980s for various purposes, according to Lynda Jones of The Logical Company in Cottage Grove, Oregon, which helps keep these antiquated systems functioning.

Because of their critical nature, many of these systems will be in continuous service long into the future, perhaps to the middle of this century. For instance, the Minuteman ICBM program, which uses DEC VAX systems for testing, recently received funding that will keep it going until 2030.

"These legacy systems are integrated into multibillion dollar systems as control or test systems," Jones says. Replacing these old systems with modern machines, she explains, would cost millions of dollars and could potentially disrupt national security.

As it turns out, replacing those systems with modern hardware designed to work like the antiquated components is a decidedly less risky venture. Jones' company is one of many that create systems to simulate older DEC minicomputers using newer, smaller, and less power-hungry electronic parts. The replacement computers emulate the exact functionality of the original hardware--and run the same vintage software--so it appears to the rest of the system as if nothing has changed.

That's important because most of Logical's customers are defense corporations refreshing old weapons technology under contract with the U.S. Department of Defense. "There are thousands of DEC systems in use for military applications around the world," says Jones, "including PDPs from the 1970s, VAXes from the 1980s, and Alphas from the 1990s."

The United States developed many fighter jet and missile systems during the Cold War era using DEC hardware for test and control functions, says Jones, because the company's minicomputers were among the very first general-purpose machines that did not require water cooling and could be used in harsh environments.

The biggest problem with maintaining such ancient computer systems is that the original technicians who knew how to configure and maintain them have long since retired or passed away, so no one is left with the knowledge required to fix them if they break.

Even if someone does know how to fix them, finding replacement parts can be tricky. Stanley Quayle, a computer emulation consultant, has seen contractors desperate to find the parts they need. "I have a prospective customer supporting a U.S. missile defense system that is buying parts on eBay," says Quayle. "Any parts they do find are as old or older than their system," meaning they’re sometimes no more reliable than the pieces they replace.

Next: A warehouse run on an Apple IIe.