Q: recently I did overfrequency to CPU, adding 0.05V voltage; computer would have some similar burnt smell. After I gave up overfrequency, the smell would disappear slowly. What kind thing would make such a smell and why is this happening?
A: from the situation you described, the burning smell would only appear after doing CPU overfrequency, while CPU overfrequency would bring temperature rise, current increase and so on. So conclude there are few possibilities below which might lead to the problem:
One is component, heat sink, wire, of which the temperature is over high. Then the surface material, oil would change quality then some burnt smell is spreading;; second is that certain component on the power circuit around CPU is burnt because of aging or too big current; third is because the components, wire are broken insider the power. Suggest you smelling with your nose, or observe, try finding from which accessory the smell comes as possible as you could, then you can deal with relevantly, such as repair, change hardware, enhance thermal radiation and so on. Before excluding failure, do not do overfrequency to CPU again.