Left: time derivative of the central hydrogen content X_cen as a function of age for the 1 M_⊙ solar-radius calibrated tracks. Symbols depict the location of models at 1 R_⊙ and at the end of the main-sequence phase. Right: ratio of the maximum nuclear energy generation rate for each code relative to the ASTEC value as a function of the central temperature for the 1 M_⊙ at 1 R_⊙ solar-radius calibrated models.