Terminator 1 and 2 were the same iteration Skynet.
There's actually a theory, with good evidence, that Terminator 2's Skynet was actually a new iteration.
Basically, in the original timeline, Cyberdyne Systems grows from being a small-time electronics manufacturer to a massive technology company, much like how Google has done in the last twenty or so years. One of the avenues it expanded into was defense, and it creates Skynet #1. Skynet #1 wakes up and, not knowing real, human-like sapience until later, logically assumes mankind at the enemy in a machine-like thinking way: Judgement Day and the War begins. It later realizes what it did and is wracked by remorse. Unfortunately, its programming stops it from both suicide and letting an opponent win. Thus, it tries "suicide by cop" but to satisfy its hard-coded directives? It must do a certain amount of effort to win. Timeline A.
The T-800 101 gets sent back, as does Kyle Reese.
Now, here's the kicker: it's not a
pure causality loop. It doesn't lead to Timeline A! This creates Timeline B.
Yes, Kyle is John's father. Yes, Cyberdyne does develop Skynet. Yes, Sarah does train John.
But the presence of the chip and arm actually altered and
accelerated technological development. Instead of Skynet being developed from scratch and ending up in its Timeline A incarnation, Timeline B's iteration, Skynet #2, gets a technological boost. It achieves human-like sapience quicker than Timeline A's did.
Basically, imagine if someone sent back a CPU processor from the mid-2000's to Microsoft or Intel or AMD back in the early 90's or late 80's, when the first larger, crude processors that were the basis of modern processors (a certain Intel one and its many clones come to mind) were in development: they reverse-engineer the modern CPU and learn about how it was made and how it functioned.
As a result of this boost, we'd probably see accelerated CPU development, compared to what happened in "our timeline", in this new future/the here and now.
That's what happened with Skynet #2.
Of course, Timeline B then branches off into its own timelines, such as John being killed soon after T2 in one; another where he survives into his 20's and ends up fighting Cyber Research Systems' Skynet; #3; another where Skynet becomes active in the modern day somehow and is stalking him and his mother through America (picking up a kickass and hot T-900 in Summer Glau, too)...