The S&P 500 is back near record highs thanks to tech stocks.

Since the index's last all-time closing high in mid-August, only two of its 11 sectors-tech and energy-have gained any ground. Still, stocks such as Nvidia, Apple and Microsoft are so big, they can drag the index up all on their own.

The S&P's worst-performing sector since Aug. 13 has been real estate, hardly surprising given interest rates have jumped, raising borrowing costs.