Near the end of Judgment Day movie the T-800 Terminator is to be melted and he says he can't destroy himself and so asks John and Sarah to press the button.
Near the end of Rise of the Machines T-850 Terminator is fighting T-X at the bunker entrance and he extracts his "power cell" and inserts it into T-X's mouth knowing that the "power cell" will shortly explode and destroy both him and T-X.
In both cases he has to destroy himself to get his mission accomplished for which he has been programmed.
Yet in the former case he refuses to destroy himself on his own and asks for assistance.
Why the difference? Do they just have different software or is there any other reason?