Not even the long-dreaded debut of $50 a barrel oil could hold down Wall Street today as technology stocks scored their biggest gains in months.

With only the flimsiest excuses for a rally, the Nasdaq Stock Market composite index had its best day since March, jumping 45 points to 1,942.20, a 2.4 percent gain.

The Standard & Poor's 500 stock index had its best day in four months, climbing 17 points to 1,131.50, a 1.5 percent gain. The gain of the Dow Jones industrial average was smaller, with the blue chip index advancing 112 points to 10,192.65, a 1.1 percent gain.

Analysts attributed the tech gains to an upgrade by JP Morgan Chase & Co. of computer chip-making equipment stocks, speculation that Oracle Corp. will be able to complete its bid to buy PeopleSoft and some minor economic data that was reported today.

But the biggest single reason for the rally may have been that it was the first day of the fourth quarter. Money managers who cleaned up their portfolios earlier in the week as the third quarter was ending, went back to the market today to put to work the cash they raised from end-of-the-quarter sales.

Whatever the reason for it, the day's rally on Wall Street totally overshadowed trading on the New York Mercantile Exchange, where crude oil finally closed above $50 a share for the first time.

Crude has gone above that mark during the day on several occasions, but each time it slipped back before the market closed. Today it stuck, climbing 48 cents a barrel to $50.12.

The impact of costly fuels could be seen in the September auto industry sales reports that came out today. They showed sales of big sport utility vehicles and trucks remain weak.

Generous incentives, however, enabled General Motors and Daimler-Chrysler to report strong gains for the month. Sales were up 25 percent from a year ago at GM and 13 percent at Chrysler.

Ford's volume, however, fell for the 10th month in a row, down 4.2 percent.