Paced by Calvin Murphy's 42 points, the Houston Rockets upended the San Antonio Spurs, 105-100, tonight to win their Western Conference semifinal, four games to three.

In the last game of series that was as improbable as it was intense, Murphy riddled the Spurs' defense while Moses Malone controlled the offensive rebounds.

San Antonio finished 12 games ahead of Houston in the Midwest Division and had the home-court advantage in game seven, but that did not seem to make much difference to the Rockets.

"The team with the biggest heart won tonight," Houston Coach Del Harris said.

The Spurs, who had lost here just seven times all season, dropped three on their court in this series.

"The home-court advantage in this series didn't mean a thing," San Antonio Coach Stan Albeck said, "and Murphy was incredible."

The 5-foot-9 guard scored 28 points in the first half to keep the Rockets in contention. "Murphy took the game into his own hands," Houston forward Robert Reid said.

Murphy did need some help, though. San Antonio held a 66-57 halftime lead. George Gervin, as usual, did most of the damage, scoring 15 points in the half.

All that changed very quickly once the second half started. Houston's defense clogged up the middle and Malone began to rule the boards.

The Spurs could score only five points in the first six minutes of the second half while Houston, using its delibreate, look-for-just-one-shot offense, grabbed the lead.

With its fast break stalled, San Antonio shot 27.8 percent, was out rebounded, 16-8, and managed to score just 12 points.

"Our people hit the boards in the second half," Harris said. "If you take away the boards, you take away the fast break."

San Antonio rallied and trailed by just one point, 97-96, with 1:43 to play, but Reid made a shot with 1:21 left and San Antonio's Reggie Johnson missed with 50 seconds to go. When Bill Willoughby sank two free throws with 35 seconds left, the Rockets had a five-point lead.

To go with Murphy's 42 points, Malone scored 21 and had 16 rebounds.

Gervin was held to six points in the second half, a half in which San Antonio scored just 34 points. Gervin finished with 21. Mark Oberding 20 and Ron Brewer 15 for the Spurs.

The Rockets, who upset the defending league champion Los Angeles Lakers in a three-game miniseries, take on the winner of the Kansas-Phoenix series.

"It doesn't matter to me who we play," said Harris. "I'm just barely over this one."