After Hewlett-Packard bought Convex, Wallach became the chief technology officer of Hewlett-Packard's large systems group. He was also a visiting professor at Rice University from 1998–1999. Prior to Convex, he was manager of Advanced Development for Data General. His efforts on the MV/8000 are chronicled in Tracy Kidder's Pulitzer Prize winner "The Soul of a New Machine". Prior to that, he was an engineer at Raytheon, where he worked on the All Applications Digital Computer (AADC). Wallach has 40 patents and is a member of the National Academy of Engineering, an IEEE Fellow and was a founding member of PITAC (The Presidential Information Technology Advisory Committee).