At any weight class, Anderson Silva is proving too tough to beat.

Silva used an electrifying performance to prove his bump up in weight class was the right one, dropping Forrest Griffin with a devastating right punch and a first-round knockout in a light heavyweight bout at UFC 101 on Saturday night.

Silva (25-4) bobbed his head as he toyed with Griffin (16-6) for the few minutes they were in the cage before putting him away at 3:23. Silva, the UFC middleweight champion, convincingly did his part to stake his claim as the top pound-for-pound fighter in mixed martial arts.

BJ Penn followed by successfully defending his lightweight crown, using the rear naked choke to make Kenny Florian tap out in the fourth round.

Penn (14-5-1) took down Florian about 80 seconds into the fourth round and kept the No. 1 contender on the mat. Florian (13-4) had no counter as he struggled to break loose.

Penn finally slapped on the submission move toward the end of the round and the crowd roared. Penn had the punishing move locked in, and Florian quit at 3:54.

"When I woke up this morning I thought, 'I've been in this thing for nine years. What the hell am I doing with myself?'" Penn said. "But this is my dream."

Silva and Penn helped usher in a new breed of Broad Street Bullies in Pennsylvania's first major mixed martial arts card in front of a ready and raucous crowd.

About 17,500 fans packed the Wachovia Center and the expected $3.5 million gate _ with ticket prices ranging from $50 to $600 _ would make it higher than any boxing card in the state's history.

"Every restaurant, everybody we bumped into in the streets, the media people here, they've all been fantastic," Ultimate Fighting Championship president Dana White said before the start of the main card. "Now I know why this place is the biggest fight town in America. This place is (pretty) awesome."

White has actively worked at expanding UFC cards outside of Las Vegas, and got a huge break in February when the Pennsylvania State Athletic Commission legalized MMA.

Philly fans responded in a huge way, going wild from the first undercard bout and proving a city known more for its deep boxing roots can root on fighters in the octagon.

"There were 11,000 people here for the first fight (of the night). That's as many as Mandalay Bay can hold," a beaming White said. "Just awesome."

The crowd roared when Penn was shown on the video screen walking into the arena. Boxer Roy Jones Jr. had a front-row seat. UFC cornerstones Tito Ortiz, Chuck Liddell and Randy Couture all watched from cageside. UFC welterweight champion Georges St. Pierre received one of the loudest ovations of the night for his big screen appearance.

Phillies All-Star Shane Victorino, who flashed his World Series ring, was there in support of fellow Hawaiian Penn.

Silva, though, stole the show.

He patiently waited to strike, and twice knocked down Griffin and struck him with repeated blows to the face.

Silva jumped on top of the octagon padding, sat, threw his body back and roared in celebration. Griffin, who received a huge ovation to the ring, sprinted out before the decision was announced.

Silva extended his record UFC winning streak to 10 straight.

Penn was more methodical in his approach

Penn came to the ring wearing a "Penn State of Mind" T-shirt and wobbled Florian in the first round. After two more underwhelming rounds, Penn delivered the move the Philadelphia fans waited all night to see.

"I love the fans, I love Hawaii," Penn said. "Want to know anything else, go to bjpenn.com."

Most of the fighters on the five-bout undercard generally failed to deliver the punishing action the Philly crowd was dying to see. Fans were lined around the Wachovia Center about 90 minutes before the first prelim fight, and the arena was nearly packed when Danillo Villefort fought Jesse Lennox in the first match.

When the two danced around the mat on their barefeet in the opening 10 seconds, the frenzied crowd started booing as if the Flyers were eliminated from the playoffs.

Silva made them forget all about the slow start with every short right hand and hard hook he threw at Griffin.