And that's why he's the specialist

Mainframe support pilot fish gets a call from his boss: A customer at a remote site says the mainframe is spewing out dump after dump of what looks like an opcode exception -- something that just isn't supposed to happen.

"So I barreled down the interstate to a customer 80 miles away that I had never met before," says fish. "I was confronted by the hardware guys telling me 'You've got a software problem.'

"Now, I always got along great with my hardware guys, but sometimes they had a bit of a limited field of vision -- if it wasn't smoking, on fire or otherwise physically busted, they didn't think it was their issue."

First fish looks at one of the memory dumps. Sure enough, it looks like opcode errors, meaning that some machine-language instructions have stopped working. How is that possible?

He knows one way: The mainframe processor's microcode might have loaded incorrectly, so it can't perform some machine-language instructions. Fish quickly rules that out, but he and the hardware guys do notice that all the failures are 6-bit opcodes, which take the longest time to process.

Or maybe something has gone wrong with the hardware that maps virtual memory to physical memory. They begin pulling those cards, but failures continue. They start pulling out other kinds of cards. Nothing seems to help, as the search for the problem's cause goes on all night and into the next day.

"Finally, we were stumped, tired and a bit ripe, having all been in the same clothes since the day before," fish says. "So we put out a call for a specialist.

"He arrived looking and smelling better than any of us, saw the array of cards and other pieces of hardware strewn about, asked what I was seeing in the memory dumps, then said, 'What was the last change done on the mainframe?'"

Turns out that just the previous weekend, a hardware change was installed. Specialist asks to see the details and look at it.

A few minutes later, after some consultation with plant engineering, specialist tells fish and the hardware guys that the new flat cables installed with the hardware change are too long, and those long-running opcodes are getting cut off before completing their electronic journey.

And sure enough, once the hardware change has been swapped out and the old cabling restored, the problem is resolved.

"The hardware guys were a bit unhappy about this whole thing," reports fish. "But I was very happy just to leave and drive the 80 miles back home, minus the suit jacket, tie and shirt. A couple hours later, a shower never felt so good."

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