[2][3][4] However, in 1950, Amdahl and Charles H. "Charlie" Davidson, a fellow PhD student in the Department of Physics, approached Prof. Harold A. Peterson with the idea of a digital computer.

[5] Amdahl and Davidson gained the support of Peterson and fellow electrical engineering professor Vincent C. Rideout, who encouraged them to build a computer of their unique design.

He left IBM again in September 1970, after his ideas for computer development were rejected, and set up Amdahl Corporation in Sunnyvale, California with major financing from Fujitsu.

By purchasing an Amdahl 470 and plug-compatible peripheral devices from third-party manufacturers, customers could now run S/360 and S/370 applications without buying actual IBM hardware.

Amdahl articulated his arguments, both orally and in three written pages,[10] on the fundamental physical limitations that he theorized would govern the performance of any special feature or mode introduced to new machines.

[citation needed] Amdahl left his eponymous company in August 1979 to set up Trilogy Systems, together with his son Carl, and Clifford Madden.

[11] With over US$200 million in funds, Trilogy was aimed at designing a wafer-scale microprocessor for even cheaper mainframes, but the chip development failed within months of the company's $60 million public offering; thereafter, the company focused on developing its VLSI technology and, when that project failed, in 1985, Trilogy merged into Elxsi, a computer maker with its own CPU design.

Andor hoped to compete in the mid-sized mainframe market, using improved manufacturing techniques developed by one of the company's employees, Robert F. Brown, to make smaller, more efficient machines.

Amdahl co-founded Commercial Data Servers in 1996, again in Sunnyvale, and again developing mainframe-like machines but this time with new super-cooled processor designs and aimed at physically smaller systems.

[14] Amdahl was named an IBM Fellow in 1965, became a member of the National Academy of Engineering in 1967 and was recognized as the Centennial Alumnus of South Dakota State University in 1986.