My northbridge sees 81°C - 177°F during 3D rendering. Do I need to upgrade the heatsink or add a fan?

Southbridge is around 50°C.

I've got the motherboard mounted to the wall, with no case. The cables are hanging off the bottom of the mobo. Therefore, the heatsinks have the fins running left-right instead of up-down.

Thoughts?

Hi,
Maybe the Thermalright HR-05 ? It's a champ in it's category.

I suppose since I don't have any expansion cards, I could rotate the motherboard so all the cables attach at the left side instead of the bottom.

I'm trying hard to avoid replacing the stock heatsink. Do I need to worry about temps like 81°C?

It's a bit high, but not extremely high. I would do something about it if the system would be unstable for some reason, but otherwise leave it alone I think.
Of course if you could arrange so that the fins would run vertical that would be great but I wouldn't say it's critical.

I use a Thermalright HR-05 myself btw. It's a good cooler but the mounting system is not great. I got it "just to be sure" since I have very little airflow in my case and it's perhaps not worth the money. But it can probably be reused for motherboards in the future so in the end it could be money well spent.