I already discussed about this on http://electronics.stackexchange.com/ and from what i got from tham is that mosfets that are on motherboards should probably last 10 years under normal use (50C all times) but that can go well beon 100C and be fine.
I wanna know did any of you had any bad experiences with no heatsinks on VRM .
depending a bit about which cpu and platform we talk about here.
For AMD AM3+ i would definitely recommend mosfet / vrm cooling. Because FX cpu´s are powerhungry, and realy heat up the mosfets.
i basicly allways recommend boards with vrm cooling, wenn it comes to unlocked cpu´s.
vrm heatsinks are just a way for motherboard manufactures to increase cost.
+1
VRM's <> MOS-FET's
a phase usually has two larger components, the MOS-FET, which is a still pretty small square SMD chip, it's actually a double MOS-FET, and the choke, which is a box mounted on the mobo next to a couple of double MOS-FET's. Those two larger components are the ones that get hot. Modern MOS-FETs are so efficient, that they actually don't get that hot, and certainly don't need cooling. Chokes can get really hot, but they are designed to work at a high temperature, in fact, it's counterproductive to cool them, because if the cooling is not constant, it will shorten the lifespan of the components because of dilatation stress, and the heat that is drawn away from the chokes, just ends up dissipated in the case, which can cause thermal stress on other components that really don't need that. Other problem with VRM heatsinks is that they cause dead spots in air circulation, which is the main cause of hot spots on the mobo. If for instance your VRM heatsink inhibits the airflow over your RAM, your RAM will fail sooner.
VRM heatsinks are just another method of programmed obsolescence. On enterprise hardware, there mostly are no VRM heatsinks, and if there are, they are of the generic electronics parts kind.
i honestly don't see what might fail on a choke. They will probably works for decades no matter what you do with them. there is simply nothing that can fail in them
Well, chokes have to absorb quite some energy, and they are electrical components. They're pretty basic components, similar to a trannie in the way they are built, but an inductor sometimes can still block a lot of energy, especially in switching power supply arrangements like in many PC's. Anyway, because they rely on coil windings that are pretty small for the wire length and on a mobo, these small chokes are cast, so there is no room for controlled dilatation, varying the temperature a lot is probably not the best idea to guarantee a long lifespan. Many mobo manufacturers nowadays sell "premium gamer" boards with small cooling fins on the chokes, and that is just madness in my opinion, for several reasons. One is that there is no way of knowing what the effect on the metal fins is on the operation of the choke as a filter for the moment, because it just isn't researched. Decades of experience with coils in guitar pickups for instance have lead to proof that material choices have considerable effects, for instance with regards to Foucault Currents. There is very little research as to the effect on metallic irregular sinks around inductors, none that I know of. Yet the probability of it affecting the operation, is pretty high by analogy with other inductor assemblies where such things have been proven.