To achieve 100x, consider what he was doing:
- writing a first person shooter (Castle Wolfenstein 3d)
- writing a first person shooter (Doom)
- writing a first person shooter (Quake)
... you get the idea.
Now, there was enormous leaps in maximal utilitilization of hardware, but do you notice a pattern? The requirements are basically fixed.
Most 10x I've achieved in a short fashion or observed was due to some similar parameters:
- the requirements were stable
- the basic problem was done before and practiced, and implementaiton was a variation/improvement of the previous
- solo or very small development team where greenfield imposed little barriers