Perhaps at least partially as a result of those efforts, the mainframe remains a core system for high volume, high transaction processes, particularly those used in large financial services companies like Bank of America Corp.

Kimberly Grim, senior vice president of mainframe engineering at Bank of America, describes mainframe systems, which handle the firm's most critical applications, as "very safe."

"We have been operating this platform for 40 years," Grim said. "It's changed a lot, and IBM has invested in keeping this platform state of the art." She said the mainframe platform can still handle high-volume work better than non-mainframe systems.

The Charlotte-based company said hundreds of its IT workers are assigned to mainframe tasks. It wouldn't be more specific on the number assigned to the platform.

IBM doesn't track the number of available mainframe related jobs, but it isn't hard to find advertisements seeking people with mainframe skills. For example, a search with the key word "mainframe" yesterday drew 97 help wanted ads on Monster.com. The jobs site said that 764 such jobs were advertised over the last 30 days. On Dice.com, a similar search produced 1,200 ads seeking mainframe experience over the past 30 days.