The Advanced Technology Airborne Computer (ATAC) was a product of Itek (a division of Litton Industries), used on US naval aircraft, and the NASA Galileo (spacecraft).
[1]: 198–201 The ATAC was built using AMD 2901 4-bit processors and had a basic cycle time of 250 ns.
The Galileo Attitude and Articulation Control System (AACSE) was controlled by two Itek Advanced Technology Airborne Computers (ATAC), built using radiation-hardened 2901s.
[1]: 201, 207 The project wrote their own GRACOS (Galileo realtime Attitude Control Operating System).
The Galileo project had radiation-hardened 2901 processors made (by Sandia National Lab) for the spacecraft.