What's your brand of rx 470? Thermal paste rarely factors in throttling the gpu unless you used a shit brand to begin with or the original paste had harden.

That's the limit of the heatsink design. As malaysia's ambient temp is quite hot, it's normal for the card to throttle back a bit when hitting 80C. Those few mhz doesnt really make a huge or noticeable difference.

Okay now that's not normal. What's your psu? How long have you had this gpu for?

Can you take a pic of the label of the psu? It's highly possible that your psu does not supply 650w at all. 19A * 12V = 228W. Your psu is only supplying 228w from the description that you gave me. The sapphire rx 470 takes in 120w. Bundled together with the rest of the system, 228w is not enough.

Model and brand of psu? According to more digging, 12v1 is used to power everything except the cpu. So the 228w is used to power your gpu and everything else including fans, motherboards etc. How old is this psu?

Any crashes before repasting?