Cooling mosfets = cpu temp drop in BIOS?

Sterculus · Jun 28, 2003

Well, I have water on a 1700+ DLT3C in my 8RDA+, and after doing some overclocking my CPU temps according to BIOS were getting really high (like mid 50's, load). My rad was cool, and so was the waterblock, but when i was reaching around I touched the mosfets near the CPU and boy they were hot. I grabbed an extra fan and wedged it about 2" away from them, blowing air onto them. Now BIOS reads my cpu temp as mid 30's load.
Tomorrow I'm going to cut up some old nb heatsinks to put on the mosfets.
Has anyone else noticed stuff like that?

R4z0r4mu5 Pr|m3 · Jun 28, 2003

got a pic?

Stedeman · Jun 28, 2003

Sounds like the heat may have “radiated” through the motherboard and warmed up the onboard temp sensor. A good reason to use on die or and external sensor imbedded in the heat sink. This could have been one of the reasons many people have had problems with their onboard readings. Good find and informative if the data is correct.

Sterculus · Jun 28, 2003

Well I just did a little 10 min test. Load, with the fan, the 'CPU' temp in the USDM was 32c, with a system temp of 26c. 10 min after I removed the fan (moving it away) the CPU temp had rocketed to 40c, but for some reason the system temp dropped to 24c. I have screenshots, but no place to host them. Once I get my digital camera working I'll take pics of the setup.
PS: In the time that it's taken me to write this message, after moving the fan back the CPU temp has dropped to 33c.

Suma · Jun 28, 2003

Got the same prob man
when i cool the vcore mosfets the temps drops magicly!!
3c-5c

using a watercooled dlt3c over a 8rda+

Sterculus · Jun 28, 2003

well, I chopped up an old nb heatsink, and put it on. After about 5 minutes at load the mosfet sink was burning hot! It's a good inch tall too, and I was touching the top. I'm trying to figure out a way to fit a fan in here somewhere.

Sterculus · Jun 28, 2003

Alright, I ghetto rigged a fan in there blowing onto the sinks. Maybe someone should watercool these little buggers sometime

Suma · Jun 28, 2003

heh,
earlyer 2day i saw some watercooled mosfets..

how did u mount the fan?

Hedgehogforprez · Jun 28, 2003

I too would like to know how you mounted the fan

Sterculus · Jun 28, 2003

I used zipties to suspend it about 3" above the mosfets

one ziptie is attached to the fan gaurd on my back exhaust fan, the other to one of the tubes for my watercooling. It's an 80mm Thermaltake I had lying around btw.

The_Merovingian · Jul 1, 2003

I had the exact same thing happen!
I mounted a 80mm fan on the side of my case facing the mosfets (to cool them and the northbridge)
And my temps went from 39load to 29 load
I use watercooling on my 2500+ cpu also.

MikeTimbers · Jul 31, 2003

Supported by its own cables wrapped around the tubing.

The_Merovingian · Aug 1, 2003

I have had this happen also, I have invannotek watercooling and before i cooled my mosfets the temps were about 44 degrees under load, not they are about 29-31

drshivas · Aug 2, 2003

Hmm, when I put a fan blowing directly on the mosfets, it raised my cpu temp. I think the fan overpowered the exhaust from the CPU HSF.

Sterculus, what size fan did you use?

Lammy · Aug 2, 2003

Use a blower fan. That would do the job better than anything else I can think of.

squeakygeek · Aug 3, 2003

I plan to hot glue a 40mm fan to the caps on either side, probably with some home-made spacers between, as I will be using heatsinks from radio shack which are a bit higher than the ramsinks I've seen. I will make a cardboard shroud to keep the air going through the heatsinks and come out on the top and bottom of the row, and to keep it from countering the cpu fan. All this is based on the assumption that it will fit once I get my SK-7.

hempp · Aug 3, 2003

yeap temp drop
here drop 9c

mad38dog · Aug 5, 2003

man am i glad i read this thread!
after setting up my new cascade block with the rest of my w/c parts over my 1700 dlt3c my temps were like 38-39c idle and up to 42-44c load. man i thought wtf, i was getting almost the same with my old volcano 7+.
cant wait to try this mosfet cooling trick.
sure hope my temps drop like yours

Veland · Aug 6, 2003

Just another reply saying the same, dropped about 5c by putting a fan on my Epox 8k7a+.

But the interesting bit, is what it does to your voltages. That moving som air around an in socket thermistor gives lower temps is hardly news, but for me, it also did some things to my voltages:

First, my +5V dropped a bit! Not good with my MB as it is extremely sensitive to 5V, but it also got a lot more stable. And under load, it didn't drop as far as before. Haven't got the precise values but something like:

Before: 5.10/4.88 After 5.05/4.91

Also, the other lines seem a bit more stable, but I don't watch them as closely..

Cooling mosfets = cpu temp drop in BIOS?

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