In the late 1960s, Gernelle earned an engineering degree at the Conservatoire National des Arts et Métiers. In 1978, he earned a Ph.D in computer science at the Pierre Mendès-France University of Grenoble.
In 1968, he was hired by Intertechnique, a company specialized in electronic measurement for aviation. There he discovered the Intel 8008 microprocessor and imagined all its potential applications. As his hierarchy didn't share his views on the i8008 development capacity, he resigned in 1972 and joined R2E, a company created and led by Paul Magneron. He designed a micro-computer to answer a request of INRA to measure agricultural hygrometry. During this project, he granted two patents. In 1973 he supported the Micral N and, with the company's growth, helped to design 20 other multi-user microcomputers for some were multi-processor one.
In 1981, the Bull company acquired R2E and he then joined the new entity Bull Micral. But the company wanted him to design IBM PC compatible machines and François Gernelle didn't agree because he thought this machine was bad designed, using an 8 bit mono-tasking mono-user i8088 powered by a poor operating system. In his mind, this kind of poor computer design was a dead-end at a time where really good micro-processors existed and offered capacity to design powerful multi-user and multi-tasking systems at medium and even low cost.