Allen was 10-for-15 from the field, including 3-for-5 on 3-pointers. In the last three games, he is 13-for-19 from behind the arc.
"I thought the difference in us the last four games was [when] they scored, we zipped it up the floor and Ray made a wide-open 3," Celtics coach Doc Rivers said. "We're setting better picks for him. We realize that to get Ray shots we have to get him open and I think our guys have done a better job."
Allen had three baskets in a row from 3-point land during his 11-point surge as the Celtics (15-2) extended an 18-point halftime lead to 73-47. Rondo assisted on all four baskets.
"When the game was over, I told him, 'When you play like that, we're a beast to contend with,'" Allen said. "I told him, 'I feed off you.'"
Rondo had 12 assists, including one on the last basket of the third quarter, a perfectly executed alley-oop to Garnett for a dunk.
It was another poor offensive night for the 76ers (7-9), who had their lowest-scoring game and first half of the season. Their previous low was 80 points in loss to Utah on Nov. 11.
"They showed us why they were world champions last year," 76ers coach Maurice Cheeks said. "Their defense stifled us."
They scored a season-low 12 points in the second quarter, as the Celtics opened a 46-28 lead. Boston opened the quarter with a 9-0 run, capped by a three-point play by Powe, to take a 33-16 lead.
Philadelphia was held scoreless until Reggie Evans converted a free throw almost four minutes in, but did not make its first shot from the field until Louis Williams' layup made it 33-19 at the 6:39 mark.
The 76ers have lost three in a row after winning five of six. The only starter to shoot better than 50 percent in the first half was Elton Brand, who was 5-for-9 for 12 points. The rest of the starting five was 6-for-20 as the 76ers were held to 33.3 percent shooting from the field.
"We've been in this situation before, having bad losses," said Andre Iguodala, who was limited to nine points. "When you have a loss like that, you can't pinpoint one person or one thing. You have to look at yourself as one whole group effort. We have to play better."
Brand scored 18 points and Williams added 15 points. Andre Miller and Marreese Speights each had 12 points. Speights was ejected with 43 seconds remaining after committing a flagrant foul on Brian Scalabrine.
The Celtics are 4-0 against Atlantic Division foes. Miller is shooting 32 percent (12-for-38) in his last three games. The 76ers have been held under 100 points in their last six games. Celtics forward Glen Davis had made 11 free throws in a row before missing the back end of a pair in the fourth quarter.
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