I think I understood your question alright. As I recall the MCP79MX was a Northbridge with integrated GPU, made by NVIDIA ca. 2010 (this may have been the last part in the MCP line before NVIDIA stopped making such parts).
Semiconductors that go into the same product tend to have similar thermal characteristics. By looking at CPUs and GPUs we can reasonably speculate (in the absence of a data sheet) how hot chips in their immediate vicinity may be allowed to run. Anecdotally, for modern chips the answer seems to be 80-85 degrees Celsius. I seem to recall that the thermal bounds were a bit higher with semiconductors built in older manufacturing processes, where the limits were more around 90-95 degrees Celsius.
Your reported temperatures (at idle, I note) are lower. You haven’t shared what they are under full load. I don’t know what the concern is which prompted your original post. That the MCP79MX could soon fry itself? Given that the part is possibly nine years old at this point, it is best to assume that, depending on duty cycle, it may be on its last legs anyhow.