He and his team had to test out so many modules so quickly that they ended up designing a special board with a small light bulb so that they could see quickly if the electrical circuit was still functioning as it moved through parts of the process.
"We literally didn't sleep for a couple of days, running things through the process, making sure we had all the right data."
In the end, he was able to isolate the problem. The design fix included covering the module with a metal cap that would allow it to survive the process.
Based on that and other work he did, Toole and his wife were treated to dinner at New York City's luxurious Waldorf Astoria Hotel and a night in its Eisenhower Suite. He received an outstanding contribution award, including a check for $1,000 presented by then-president Tom Watson Jr. and Watson's mother.
"I might have been 26 at the time," he said.
The System/360 also marked the first time that mainframes were compatible with each other. That meant a business could buy a small system and when it outgrew it, buy a larger one with the knowledge it could still run the same software and use the same peripherals.
That presented a whole different set of challenges for IBM. "These individual plants and labs that had never worked together before now were forced to. All the interfaces had to get aligned, all the software had to be portable," Toole said.
It was a huge bet for IBM. The company invested some $5 billion to develop the System/360, equal to almost double its annual revenue at the time.
"It was just a monumental task, with everyone working on it," Toole said. "It was extremely exciting, working around the clock and through the calendar."
He's modest about the "small" role he played, but he would go on to do well at IBM. He became a lab director, a division president and eventually general manager for IBM Technology Products. His son, Pat Toole, is general manager of the IBM mainframe business today.
The mainframe was an immediate success, Pat Toole Sr. said. "We were not only sold out for a couple of days, we were sold out for a couple of years."
Some customers ordered systems without being sure they would even need them when delivery time came around. There were also speculators, Toole said, who ordered systems hoping to sell the contract for a markup later on.
"One of the good problems was we got a lot of orders. One of the bad problems was, we didn't know how many of them were real," he said. IBM sent teams out to check which orders were valid.
Toole remembers the 360 launch day at IBM. "We had an all-hands meeting and they made a special movie to show everyone." But his best memory is of the "second launch" a few months later at IBM's stockholder meeting at the Endicott, New York, country club.
It was a sunny July day, IBM's board was there and people milled around large tents eating and drinking. They were shown into an auditorium, a few hundred at a time, to watch a film about the 360's development and of customers talking about how they planned to use it.
Toole was assigned to accompany Gil Jones, then head of IBM World Trade, IBM's international arm. He answered Jones' questions about the 360 and took him on a tour of the plant.
"You felt like you were in the right place," he said.