Steven Mills, an IBM (NYSE: IBM) veteran since 1973, stepped down as executive vice president of software and systems, Big Blue disclosed Monday. Mills once turned down the chance to become CEO at HP, according to Reuters.

Mills is 64.

The news triggered a research note from UBS, which reiterated a “neutral” rating on Big Blue shares.

According to Wall Street Insider, UBS Analyst Steven Milunovich pointed out IBM’s software business has struggled.

“He apparently stayed on beyond the typical age 60 retirement age at [chair, ceo Ginni] Rometty’s request. He is a giant in the tech industry, best known for growing IBM’s software business both organically and through acquisition,” Milunovich wrote.

“In recent years, however, IBM Software has disappointed relative to his expectations a few years ago of 5% revenue growth and double-digit pretax gains. In 2015 software revenue will be down about 3% in constant currency, and reported pretax income could be off by almost $2bn the past two years from $11.1bn in 2013 to an estimated $9.2bn in 2015.

“IBM is getting picked off by upstarts like ServiceNow, and investors wonder if there is need for middleware like WebSphere in a cloud world. We don’t know if there is a direct replacement for Mills, who recently ran both software and hardware, but new blood may be helpful.”

eWeek acknowledged Mills’ achievements over four decades:

“Known as a fierce competitor true to Big Blue, Mills promoted IBM’s solutions at any opportunity. He did not mind calling a competitor on the carpet for missteps, yet he also saw the value in partnering with competitors when necessary and forming alliances. In an early display of this, back in the SOA web services era, Mills once shared the stage with then Microsoft chairman Bill Gates to demonstrate IBM’s and Microsoft’s web services interacting with each other.”

Mills helped form the IBM Software Group in 1995. He also was involved in more than 30 acquisitions over the past 15 years.

Reuters reported in 2010 that Mills turned down an offer to lead HP, citing two sources.

IBM employs several thousand people in RTP and across North Carolina.