If there were any hopes lingering in their minds, the moment of truth for the Houston Rockets came with 11 minutes left in the fourth quarter of the Boston Celtics' 114-97 title-clinching victory today in Game 6 of the NBA championship series.

It came when Boston forward Larry Bird retrieved a loose ball in the lane and made the kind of move that has made him most valuable player in the league three straight times. It also has made him the playoff MVP two times in three years, including today, after he had 29 points, 11 rebounds and 12 assists.

The 24-second clock had dwindled to three. Bird made a ball fake, then dribbled away from the basket and into the left corner, where he drilled a three-point field goal as the horn was sounding. That made the score 87-61, Boston.

"You have to do something like that so you can break a team's back," he said. "I was just trying to get the series over as quickly as possible."

Surely the game was over long before that shot, but there was no mistaking the importance of a brilliant play by the best player on the best team in the NBA this season, which won a record 82 games, including playoffs.

The Rockets needed a strong early effort to quiet a hostile Boston Garden crowd. The Boston fans repeatedly booed 7-foot-4 Ralph Sampson, who had been ejected from the fifth game after throwing the first punches of a brawl. But neither Sampson nor his teammates were on their game and Boston led, 55-38, by halftime.

Sampson scored only eight points, two in the first half when he missed seven of eight shots, but there were no incidents with Boston players or fans. Akeem Olajuwon led Houston with 19 points and 13 rebounds.

Forward Kevin McHale scored 29 points for the Celtics, who placed all five starters in double figures and won their 41st consecutive home game, ending the season with a 50-1 record in the venerable Garden.

Very few in the assemblage gave Houston much chance of extending the series to a seventh game, and the Rockets' chances lessened considerably when Sampson had his second poor outing in the three games here. In the series opener, he shot one for 13 from the field and scored two points. Today, he was four for 12.

"I didn't have a good game at all," said Sampson. "I figured the refs would call the game tight. I wanted to stay in the game and not get into a pushing and shoving match."

With Sampson quiet, Boston led by 17 points at intermission, a margin built largely by Bird, who went into the locker room with 16 points, eight rebounds, eight assists and a mild case of anger.

"I got a little upset in the second quarter," he said. The day before, Bird promised to be the catalyst for his squad, but: "I wasn't getting the ball enough. I could've iced the game before the first half was over."

Although there still was plenty of time remaining, the game -- at least its competitive aspect -- had ended. Boston ran off a 24-10 streak to conclude the opening half, but that wasn't as impressive as its 30-16 first-half advantage in rebounds.

"It was like we were wearing their uniforms and playing like them and they were in ours and doing the things we did," said Rockets Coach Bill Fitch, referring to his team's 111-96 victory in Game 5, in which Houston held a 56-37 rebounding edge.

Overall, Boston, which would push its lead to 30 points in the second half, provided the Rockets with very few moments for their highlight film.

There was the 51-second span in the opening quarter when Olajuwon tried to do for his team what Bird did for Boston. On three consecutive Celtics possessions, the 7-0 forward/center sneaked behind Bill Walton and poked the basketball away. On the first two occasions he drove the length of the floor for dunks, the third time he fed Rodney McCray for a layup.

A plus for the Rockets was the Celtics' surprising difficulty with free throws. In the first quarter, Dennis Johnson and Robert Parish missed two foul shots each, Bird missed one. In the first half, Boston was 11 for 21 from the line.

But even that negative statistic was a positive, according to Bird. "Any time our guys miss that many free throws I know they're pumped up," he said. "They're trying hard so you can't say nothing to 'em."

For a team that wore its emotion on its sleeve throughout the season, the Celtics were relatively mute in the hours leading up to today's game. During practice Saturday, the normally loquacious McHale limited his comments to a terse two minutes.

The all-business attitude manifested itself in other ways, too, said Coach K.C. Jones.

"I had to call off our practice," he said. "I was just going to go five baskets and a half-court scrimmage but these guys went at each other like Muhammad Ali and the gorilla.

"I've never seen anything like that in all the time I've been here. The intensity level was just incredible. The guys were irritable. A guy would walk through the locker room and someone would say, 'Who the hell is that?' and it would be the trainer."

In Houston's Game 5 victory Thursday, Boston felt it had been repeatedly burned, both by Olajuwon, who had 32 points and 14 rebounds, and Reid, who passed for 17 assists. "They were the pressure points that we had to do something about," said assistant coach Jimmy Rodgers.

Indeed, the Celtics made a pair of defensive switches today, putting Parish on Olajuwon and Dennis Johnson on Reid. Apart from his spurt at the conclusion of the first quarter, Olajuwon was quieted. Reid scored 12 points with six assists, but in the crucial first half he had two of each.

"Every time he touched the ball I was supposed to be in his face," said Johnson. "I don't think he really got into the flow until about the last six minutes."

By then it was far too late to do Houston much good. And that was mainly because of Bird.

"There wasn't an area of the game in which he didn't play fantastically," marveled Rodgers. "It's not as if we have to ask him to do things, he volunteers, and whatever he wants to do is good by us."