"This quarter we faltered," IBM CEO Arvind Krishna said in a letter to investors released Tuesday after worse than expected quarterly results

CEO Arvind Krishna writes letter to investors to explain "performance shortfall"

“What played out was worse than our expectations,” CEO Arvind Krishna warned investors.

IBM shares tumbled sharply in premarket trade after the company flagged weaker-than-expected second-quarter results, missing both profit and revenue estimates. Management…