IBM is quadrupling the AI horsepower in its new mainframe chip, and its launching an AI add-on card for customers who need more power.While International Business Machines (IBM -0.14%) now derives most of its revenue from software and consulting, the decades-old mainframe business is still an important part of the century-old tech giant. Industries like banking and insurance still depend on the hulking systems, known for their extreme reliability.IBM tends to launch a new generation of mainframe system ever ...