Fanless CPUs - What about the northbridge / VRMs?

[smeezekitty]

So I had an older motherboard around here along with a Athlon X2 3800+ that I got pretty cheap.

Just out of curiosity, I mounted a heatsink without a fan on the CPU and booted it beched without a case.

I booted a Xubuntu live cdrom with a spare cdrom drive.

It worked ok and the CPU temp was hot but not intollerable. It was around 45c idle and in the 50s under moderate load. I am sure it would overheat with full load but I was using a relatively small heatsink for passive cooling.

The problem I had was not the CPU though; but rather it was the northbridge and VRMs. During operation, I could keep my hand on the CPU heatsink but the VRMs and northbridge were very hot - almost too hot to touch within 10 minutes.

When using a standard fan cooler, they are barely warm.

So this brings the question: How do people that either use passive cooling or water cooling keep the NB and VRMs cool with the much reduced airflow around the motherboard?

 

[vmem]

So I had an older motherboard around here along with a Athlon X2 3800+ that I got pretty cheap.

Just out of curiosity, I mounted a heatsink without a fan on the CPU and booted it beched without a case.

I booted a Xubuntu live cdrom with a spare cdrom drive.

It worked ok and the CPU temp was hot but not intollerable. It was around 45c idle and in the 50s under moderate load. I am sure it would overheat with full load but I was using a relatively small heatsink for passive cooling.

The problem I had was not the CPU though; but rather it was the northbridge and VRMs. During operation, I could keep my hand on the CPU heatsink but the VRMs and northbridge were very hot - almost too hot to touch within 10 minutes.

When using a standard fan cooler, they are barely warm.

So this brings the question: How do people that either use passive cooling or water cooling keep the NB and VRMs cool with the much reduced airflow around the motherboard?

north-bridge and VRMs can typically tolerate upto 80-90C or higher, far beyond "hot to the touch" temperatures. there are also water-blocks for VRMs/NB, and most cases have air-flow, which is better than benching open-case

 

[smeezekitty]

Thanks for the reply. Too bad that the NB and VRMs need airflow like that because the passive CPU cooling was working surprisingly well. With a bigger HS and underclocking you could have a very usable silent system.

I am surprised how much difference in temperature a small portion of the air off of a CPU fan makes.

There are probably also motherboards built for enthusiasts that tolerate alternative cooling better.

This is not so much of an enthusiast board, but for $8 I cannot argue much LOL

 

[vmem]

Thanks for the reply. Too bad that the NB and VRMs need airflow like that because the passive CPU cooling was working surprisingly well. With a bigger HS and underclocking you could have a very usable silent system.

I am surprised how much difference in temperature a small portion of the air off of a CPU fan makes.

There are probably also motherboards built for enthusiasts that tolerate alternative cooling better.

This is not so much of an enthusiast board, but for $8 I cannot argue much LOL

to me, a quiet system is fine. get some quality fans and let them spin slowly for a gentle breeze and all should be well. Noctua fans push a lot of air at slow speeds, so do Scythe gentle typhoons (the 1400rpm or slower ones are almost silent)

I think enthusiasts boards have larger heat spreaders on the VRMs, and the VRMs are sometimes of better quality (not always). you can always add buy aftermarket heat-spreaders and stick them onto the NB etc with thermal tape