Clue: In 2001 he computed a bit less than 45 minutes? (3)
Answer: HAL
Explanation: Definition: In 2001 he computed
The name of the computer in the film *2001: A Space Odyssey* – I think the wordplay is a truncated HAL[f], referring to the 45 minutes of the halves of a game of football ("a games of two halves")