BEIJING — Seeing wasn't believing. It took technology to confirm Michael Phelps won his seventh Olympic gold medal in the 100-meter butterfly with a finish so close it fooled the human eye.

Anyone watching in the jammed-to-the-rafters Water Cube or on television thought Milorad Cavic of Serbia had pulled a monumental upset Saturday morning, spoiling Phelps' chance at breaking Mark Spitz's vaunted record of seven golds in a single games.

The Serb did, too.

"It was kind of hard to see," Cavic said. "I know I had a long finish and Michael Phelps had a short finish."

Even Phelps' coach, Bob Bowman, was in doubt.

"I wasn't sure he was going to get there," Bowman said.

Phelps — and everyone else — only knew he'd won by checking the scoreboard, where a "1" appeared by his name and a "2" by Cavic. They were separated by a hundredth of a second — the smallest margin measured in swimming.

It was so close and impossible to detect on regular-speed replays that the Serbian delegation filed a protest, triggering video and timing reviews down to the 10-thousandth of a second by FINA, swimming's world governing body.

"It was very clear that the Serbian swimmer touched second after Michael Phelps," said referee Ben Ekumbo of Kenya, a member of FINA's technical committee. "One was stroking (Phelps) and one was gliding (Cavic)."

Ekumbo confirmed Omega's electronic timing system also was in "perfect order," having been tested as usual before each competition. Large touchpads hanging in each lane stop the clock when triggered by a swimmer's touch — in this case Phelps' arms crashing into the wall.

The timing review by Ekumbo and a FINA commission member confirmed Phelps' time of 50.58 seconds, his only victory in these Olympics that wasn't a world record. Cavic touched in 50.59.

The main timing system is powered by cable and a backup system by battery. Both systems recorded the same times for Phelps and Cavic, Ekumbo said.

Any suggestion that FINA called Phelps the winner so he could tie Spitz's record and have a shot at winning an eighth gold in Sunday's medley relay was dismissed by Ekumbo.

He said the Serbians were allowed to review the frame-by-frame footage, although the rules don't require it.

"They accepted the ruling because it was not the human eye making the judgment," Ekumbo said. "It was the footage."

Branislav Jevtic, Serbia's chief of mission in Beijing, said the protest was short-lived.

"The video says (Phelps) finished first," he said. "In my opinion, it's not right, but we must follow the rules. Everybody saw what happened."

Cornel Marculescu of Switzerland, FINA's executive director, confirmed Ekumbo's findings.

"Michael Phelps is the greatest ever," he said. "There is no doubt the question was for him to share or not to share first place. There is no doubt the first arrival was Michael Phelps."

IOC member Kevan Gosper said FINA's decision was based on who touched first.

"I don't think there's any reason for a protest," he said. "In the old days the judges ruled. Now it's the timers."

Cavic watched a replay afterward and said he accepted the results, although the Serb noted, "Technology is also imperfect. The hand is quicker than the eye."

Bronze medalist Andrew Lauterstein of Australia had yet to catch a super slo-mo replay, but he heard other swimmers reacting with shock and disbelief at the results.

"They couldn't believe Phelps got there, and I'm sure I'll feel the same way," he said.

Phelps didn't know the Serbs had protested, but he defended the results.

"The timing system says it all," the American said. "There hasn't really been an error in the timing system that I've ever heard of. The scoreboard said I got my hand on the wall first."

He later watched a frame-by-frame replay on computer.

"It's almost too close to see," he said.

Cavic, who speaks impeccable English and trains in Florida, said he came in simply wanting to earn a bronze medal, so he wasn't bitter about missing out on the gold.

"From the heart, I'm really enjoying this," he said. "I'm not about fighting it. I'm not angry at all."

But the Serb knows the debate isn't over.

"People will be bringing this up for years, saying, `You won that race,"' he said. "If we got to do this again, I would win it."