In 1980, Dean was invited to join IBM as an engineer. Despite his new position, he continued his education and received a Master’s Degree in Electrical Engineering from Florida Atlantic University in 1982. In his capacity as an engineer for IBM, he didn’t take long to make a big impact, serving as the chief engineer for the team that developed the IBM PC/AT, the original home/office computer. Along with his colleague Dennis Moeller, he developed the Industry Standard Architecture (ISA) systems bus, a component that allowed multiple peripheral devices such as a modems and printers to be connected to a PC, thus making the PC a practical and affordable component of the home or small business office. Dean would own three of the original nine patents that all PCs are based upon. Dean followed up with PS/2 Models 70 or 80, and the Color Graphics Adapter (which allowed for color display on the PC).

Despite his enormous success, Dean realized that there was more to learn and more than he could achieve, so he entered Stanford University and in 1992 received a Ph.D. in Electrical Engineering. Five years later he was named as the director of the Austin Research Laboratory and director of Advanced Technology Development for the IBM Enterprise Server Group. Under his leadership, in 1999 his team made several significant breakthroughs including the testing of the first gigahertz CMOS microprocessor. With this great success he was named the vice president for Systems Research at IBM’s Watson Research Center in Yorktown Heights, New York, then as a vice president in IBM’s Storage Technology Group, focused on the company’s storage systems strategy and technology roadmap. He was later named vice president for hardware and systems architecture in IBM’s Systems and Technology Group (STG) in Tucson, Arizona and finally the vice president of the IBM Almaden Research Center in San Jose, California.