Are aftermarket heatsinks needed on the VRM area?

[GeezerMan]

I was involved in a discussion in another forum regarding VRM cooling. The question I had was about some PC builds I did last year with a 125 watt AMD 940 X4 in a Gigabyte GA-MA785GM-US2H mATX board with 4 phase power and no heatsinks in the VRM, and a aftermarket tower CPU heatsink with 120mm fan. These PCs are being used just for office work, so I would be surprised if they get over 40% core usage very much.

here is what I was advised: That even with no overclocking and with tower coolers, heat on the VRM area would get hot. The VRM gets little air flow with the tower coolers and actually better VRM airflow with the stock coolers. And boards with 4 phase power and no heatsinks on the VRM, it would hurt the lifespan of the board with the 125 watt CPUs.

What do you guys think of this? I don't want these builds crapping out on me a year from now. Should I install aftermarket VRM heatsinks?
Thanks

 

[VirtualLarry]

I don't know if you need VRMs, but I know that I built an AMD gaming rig based on the same mobo, and an X3 720 BE, that was unlocked to a quad-core, and overclocked to 3.2Gh.

It got shipped down to florida, and it started flaking out a bit.

So I don't know if it was the VRMs or what.

 

[john3850]

Every intel mb I had from the first C2d to present had a very hot area around mosfets.
I always added 1 or 2-60-70mm fans to the area to help cool the heatsinks around the cpu.
Because I use water I just add some tie backs to the hold down bracket screws to mount the fans,simple cheap and cooler.

 

[happy medium]

What do you guys think of this? I don't want these builds crapping out on me a year from now. Should I install aftermarket VRM heatsinks?

I've done some research on this subject also.

Read this...
http://www.overclock.net/amd-cpus/943109-about-vrms-mosfets-motherboard-safety-125w.html

Check for your motherboard here.... It seems your board is good for 125 watt cpu's with no overclocking.
http://www.overclock.net/amd-motherboards/946407-amd-motherboard-vrm-information-list.html

I would install the heatsinks on your board if using a stock 125 watt cpu and aftermarket cooling, unless your case has excellent airflow in the vrm area..
A reference cooler does push air directly on your vrm's and would not require heatsinks if you are running your 125 watt cpu at stock.

I do caution you that a stock 125 watt x6 cpu will require heatsinks no matter what cooler you use, with your peticular board.

 

[TurtleCrusher]

Im of the thinking that if you want it to last, put a heatink on it. I just learned voltage regulators and mosfets a few weeks ago and man, they can open or short with full operating voltage applied in no time. Vrms get blistering hot even with minimal load applied. With just a tiny crinkle heatsink around it heat dissapated so much better that you could safely touch it without a serious burn.

If you get a board without, at least get good airflow around it.

 

[sangyup81]

I second that. If you have an extra fan lying around, just have it blow down on the VRMs. If you don't, the money is better spend on MOSFET heatsinks.

 

[GeezerMan]

I second that. If you have an extra fan lying around, just have it blow down on the VRMs. If you don't, the money is better spend on MOSFET heatsinks.

Thanks for all of the responses guys. I'm thinking a side fan blowing onto the VRM area will do, especially since these PCs are being used for general office work, so they probably run around 5% to 20% usage on average.

 

[frostedflakes]

They do get hot, but those power MOSFETs are also designed to handle high temperatures, 100°C+ isn't going to kill it quickly like those temperatures might for a CPU. Rated operating temperature is typically up to 150-175°C I believe. Of course the cooler the better, though, higher temps will hurt longevity with any integrated circuit.

It probably depends on the quality of the VRMs as well. I know a lot of MSI boards, for example, have had a lot of problems with blown VRMs whereas other boards haven't as much.

One potential solution if you're concerned about it is undervolting the CPU. My X4 955 can undervolt to about 1.23V and remain stable. So I'd think something like 1.25V would work well for the X4 940s since they run 200MHz slower, but be sure to stress test and verify stability on all the systems if you do undervolt, some may need more voltage.

 

[BonzaiDuck]

If you have the patience and the time, there are one or more things that can be done.

You can use the Arctic-Silver 2-part epoxy -- Alumina(?) -- to glue heatsinks on the components. This is a permanent installation, and if you're not careful, you can actually shorten the life of the components if you fail to keep the paste off conductive metal.

You can contrive to give your case low-noise, high CFM pressurization, and then create two separate ducts each ending in a thermally-controlled 120x38mm exhaust fan with a capability to run up to 2,000 or 2,500 RPMs.

The first duct, which can be augmented by a pusher-fan, flows air through the CPU cooler and out one exhaust.

The second duct pulls air from an assembly that looks like a department-store shirt-box, cut to fit the bottom fin of the tower heatsink and drawing air from all over the top half of the motherboard. How you port this second duct to another 120mm fan should not be too much of a challenge, and can be built in nicely-cut and folded foam art-board, or Lexan cut and glued (with the proper glue -- check a hobby-supply store), and/or shaped with a heat-gun over whatever type of mold you can make without a lot of time and trouble.

A 5"-dia tube, for instance, might be made by slowly molding a Lexan rectangle around an aluminum-covered "Old Fashioned Quaker Oats" box (which is shaped like a cylinder).

I haven't been too enthused about an elaborate ducting project since the mobo-makers put heatpipe sinks on the motherboard components and more elaborate designs improved with better cooling. But the more airflow over the motherboard, the better . . . .

 

[GeezerMan]

Good info here guys, thanks alot. I sure did not give the VRM area much thought in the past since I don't overclock. I just thought that a 4 phase power board would be OK at stock settings. I also thought that with aftermarket cooling everything was better, but I did not think that the HSF that come with the CPU might actually cool the VRM area better. Interesting.
My main PC is a Gigabyte 8 phase power board, that I thought was overkill, but after reading about the failures with 4 phase boards and 125 watt CPUs, I think I will continue to use the better boards.

 

[Stuka87]

Most MicroATX boards don't have heat sinks in that area. But if you look at just about any gaming board, they have nice big heat sinks.

But for normal use, I would not be concerned, provided the board is rated for a 125W CPU. And not all mATX boards are, so be aware of that.