I made a little analysis and observation, due to which I came across an interesting fact that Irkens do not use artificial intelligence as we humans do, they using Vortian brains in wide application in cyber technology
they using them not only for stock knowledge, Zim's base also controls with the brains, the origin of which is not stated, but it will be logical that it was also Vortian brains, bc they are the most versatile and convenient to use, like other parts of their organism (like Vort-dogs) I guess...
based on this, it can be suggested that the Vort's brain will resist control and application, so I think that Irkens install special programs and restrictions to control them.
besides, since the Irkens use the Vortian brains in almost all cyber technology, it means that Sirs are also controlled by their brain? yeah, that's quite logical, and I think that they use a younger brain, maybe even a child's brain, bc they don't need to think, they are created as an assistant to carry out the orders of their masters, as well as to analyze what is happening on an alien planet, atrophying their emotional part, as it was in the series with the changing Gir's settings...
still why Sirs also has a brains? I'm more than sure that they are also controlled by the brain, based on that episode where Gir temporarily replaced the brain of the Zim's base computer.
Also Gir is an old Sir's model, so we can't know how the true Gir's model behaves in general, but we can notice that he behaves like a real child, and also unlike new Sir's models he has a mouth and voice, which tells us that the previous model could hold a conversation with its owner until Irkens decided to remove this function, apparently due to old model's overload (remember that Gir switches off and even explodes from emotional and mental overload).
and where then brains puts in when we know that Gir's head is empty — it's their body, the size is also perfect for them also as a case after the head explodes or is removed, this does not pose a serious threat to the robot assistant's work.
about Zim's base Computer brain I can tell that Zim had two Computers in the project and first happily died in the first season of the show. this is already a theory, but I want to assume that even their behavior was different: The first ignored Gir as best he could, and was also surprised that he was able to cough or express any emotions. The second, after replacement of the previous one is more serious and even rude, he refuses Zim's petty requests, although for Gir he allows him to do whatever he wants as for a small child.
So, I was interested to make a fan-designs of true bodies of Zim's Computers and Gir too:
and another one sketch with Computer and Gir if they were a Vorts:
I'm sure, that Computer perceives Gir as a real child, which is why he gives him the freedom to do whatever he wants on the base, then silently cleans up everything he did, perhaps because he doesn’t know how to treat children, but he treats quite tolerant of this, for which I would like to give him respect
Gir, in turn, perceives the Computer most likely as an older brother or a kind uncle.
I hope this information was useful and interesting for you, I'll be glad to see your opinion and additions on this theme.