The hosts added a further 68 runs to their total on the third morning, extending their overall lead to 479, before declaring their second innings on 275 for three.
Chasing a notional 480, Pakistan reached 47 for one by lunch, with Jamshed making an unbeaten 40 off 62 balls with seven boundaries, but it will do little to change the ultimate outcome of this match.
Of more importance was the loss of opener Mohammad Hafeez for just two - he made only six in the first innings - as he was caught behind off Vernon Philander.
While Jamshed punished the South Africa bowlers at one end, Azhar Ali proceeded at a far more sedate pace, reaching five off 27 balls before the break.
Jamshed's efforts at least ensured Pakistan did not have to worry about beating their first-innings tally - their lowest ever Test score of just 49.
Earlier, AB de Villers, resuming on 63, swiftly advanced to his fifth Test century from 117 balls, while Hashim Amla moved onto 74 before they were called in by captain Graeme Smith.