Pac-Man (Midway, with speedup hack) refers to a version of Pac-Man released by Midway featuring a speedup hack. The 'speedup hack' likely involves altering the game's code to make Pac-Man and/or the ghosts move faster than in standard versions. This change significantly impacts the game's difficulty and the overall gameplay experience. Midway's role was primarily distribution in this case, while the 'hack' would come from an individual or group altering the original code. 

Pac-Man (Midway, with speedup hack)

Pac-Man (Galaxian hardware, set 2)