The Boston Celtics staged their second straight miracle comeback tonight to topple the Philadelphia 76ers, 100-98, before 18,276 startled fans at the Spectrum.

The victory evened their Nba Eastern Conference championship series at 3-3, forcing a deciding seventh game Sunday at the Boston Garden.

In the most physical game of the series, the Celtics overcame a 17-point second-quarter deficit and outmuscled the usually intimidating 76ers in the fourth quarter.

"They just beat us on the boards terribly," said Philadelphia Coach Billy Cunningham. "There was nothing we could do with them. They just wanted the ball more than we did, and when it went up, they went up and took it."

Of the 30 points Boston scored in the final quarter, eight came on offensive rebounds.

The game still came down to the final seconds.

Larry Bird, the game's high scorer with 25 points, made a long jump shot to put the Celtics on top, 98-95, with 64 seconds remaining.

Andrew Toney, got the Sixers to within one, 98-87, 12 seconds later with a 20-foot jump shot.

The Celtics were trying to run a play for Bird on their next possession, but Toney stole the ball with 30 seconds to play. Toney, the 76ers' leading scorer in the series, tried to do it by himself, but his layup attempt with 14 seconds left was blocked by 6-foot-11 Kevin McHale, who also managed to gather in the loose ball.

The Celtics played keepaway until Julius Erving fouled Cedric Maxwell with two seconds left. Maxwell made two free throws for a 100-97 Boston lead.

After a Philadelphia timeout, Tiny Archibald intentionally fouled Erving to prevent the 76ers from getting a three-point shot. Erving missed the first free throw and made the second to account for the two-point margin of victory and send the series back to Boston.

"I was just trying to take the ball to the hole," Toney said. "i saw daylight so I took it. The Boston guy was just able to get a hand on it."

The Boston guy was rookie McHale, who had blocked three other 76er shots earlier. He was in the game because 7-foot Robert Parish had fouled out after scoring 21 points, getting 10 rebounds and blocking two shots.

"I had (Darryl) Dawkins pinned behind me and I wanted Toney to commit himself," McHale said, "so I faked out at him and he pulled up, I laid back and, when he shot, I went after the ball. I remembered what Bill Russell always said about blocking a shot and keeping it in play and I consciously tried to do that."

He succeeded and, after blocking the shot, grabbed the ball and flung it upcourt to Archibald.

Cunningham called this "the poorest officiated game I've ever seen in the playoffs."

Officials Jack Madden and Paul Mihalak did have their hands full. They called 64 fouls and even had to go into the stands to break up a brawl between Maxwell and some 76er fans.

Four minutes into the third period, Maxwell went into the seats trying to retrieve a loose ball. As he was walking back to the court, a 76er fan stood and started berating him and pointing at him. Suddenly, Maxwell turned and charged the fan, pummeling him to the floor near the Celtic bench. His Celtic teammates poured in to aid him and order was quickly restored.

Maxwell wasn't penalized.

It was established early that this wasn't to be one of Erving's better games. He missed his first five shots and never really got into the flow. He made only five of 17 shots and scored 16 points.

Dawkins picked up the slack. He scored nine of Philadelphia's first 11 points to get them off to a 31-18 first-quarter lead.

The Celtics closed to within nine at halftime, but Dawkins scored the first six points of the third period to get the lead back to 15, 57-42.

Dawkins finished with 24 points.

"Whatever I got, it wasn't enough," Dawkins said. "This is still the Doc's team. He missed a couple of shots early and he told me to go ahead and work with it, so I tried to take charge."

Bird was cold in the first half, too, going two for 10, but he found the range in the third period with 11 points as he, Maxwell and Parish led the Celtic comeback. They trailed by only three, 73-70, going into the final 12 minutes.

The score was tied four times and the lead changed seven times in the period.

"We played basketball in the first 16 minutes and then only played for a minute or two the rest of the way. There's no way you're going to beat this team playing like that," Cunningham said.

The Celtic victory snapped an 11-game losing streak for them at the Spectrum.

The winner of Sunday's game will face the Western Conference champion Houston Rockets with the first two games of that seven-game NBA championship series to be played in either Boston or Philadelphia Tuesday and Thursday.