As IBM gets set to report second quarter earnings after the bell today, investors may be losing patience.

Analysts expect Big Blue to report its 21st straight quarter of declining revenue growth as its big investments in new technologies — like cloud computing and artificial intelligence — continue to be outweighed by its slowing legacy businesses.

And while tech has been one of the best performing sectors this year, IBM has fallen nearly 8 percent.

Pressure is mounting on CEO Ginni Rometty. She's in year six of her turnaround plan and analysts say the cornerstone of her tenure — Watson AI — has yet to improve IBM's bottom line. Rometty has said that Watson is a "silver thread that runs through a lot of things" at the company.

But IBM doesn't break out numbers for Watson, so it's difficult to test her assertion. A recent report from Jefferies puts the low end of Watson and associated revenue at 3 percent of projected 2019 earnings. Even In its bull case, Jefferies puts it at a mere 5 percent. Barclays thinks it's time to cut its full-year outlook as the "narrative becomes tedious" and notes the company has shown "a lot of investments in next-gen tech but ... little revenue impact."

Other analysts, though, say the turnaround is going to require more patience. Brian White at Drexel Hamilton says, "the cognitive world hasn't taken off yet." He said the use cases for Watson are still relatively small, and in a few years "we should hear more about it." White also points to what IBM calls "strategic imperatives" (its next gen tech) which grew 13 percent in the previous quarter and made up 40 percent of total revenue in 2016.

But patience is already running thin among some investors. If IBM notches another quarter of declining revenue, it may test it further.