Traders emboldened by a scorching dose of tech earnings sent the Nasdaq 100 index to its biggest rally in 19 months on Friday. About $185 billion was added to the market cap of the five largest companies alone, a rally reminiscent of the glory days of the tech bubble. The surge put the Nasdaq 100 up 28 percent in 2017, its best show relative to the S&P 500 index since the start of the bull run.

So large was Friday's rally in the biggest companies — Facebook, Amazon.com, Alphabet, Microsoft and Apple — that without them, the S&P 500's gain went from 21 points to almost zero.

That phenomenon is a reprise of the first six months of 2017, when the FANG group was responsible for about one-third of the broader market's advance. Back then, speculation was rampant that a sell-off in the leaders would torpedo the bull. A problem for the thesis now is that the stocks did sell off, dropping four straight weeks in August, while the S&P 500 kept going up.

"There was a time in the market when they were the primary drivers, but that's not the case now," said Krishna Memani, chief investment officer at Oppenheimer Funds.

The Treasury will sell $42 billion of three-month bills and $36 billion of six-month bills Monday. They yielded 1.13 percent and 1.28 percent in when-issued trading. It will also sell $50 billion in a cash management bill Monday and four-week bills Tuesday.

— Bloomberg News