Thermally controlling a Zalman VF-700cu

wumpus · Post by **wumpus** » Wed Jul 06, 2005 9:38 pm

I recently purchased a 7800gtx*, and after running the surprisingly decent stock cooler for a while, I bought a Zalman VF-700cu to install on it.

The results are summarized on page 3 of this thread. Here's the reader's digest version: forget 5v under load, but somewhere between 7v and 12v is fine for cooling a 7800gtx. It does perform better than the stock cooler, as you would expect, but it's not earth-shatteringly better (think 5-7c better under load, with lower average temps and faster heat dissipation.

One disappointment, though: I couldn't figure out a way to make the 700cu temperature controlled. Like the stock fan, ideally it should slow down when not under load, and speed up when under load.

The 7800gtx has a 4-pin pulse wave modulation fan header which is totally useless for connecting the 3-pin zalman. I installed a VF-700alcu on a 6600gt last week and it had two pins (black and red) which worked-- I just removed the female plastic connector from the card and stuck the 3-pin zalman connector on it so the black and red wires matched up. Worked great, but this isn't possible on the 7800gtx.

I actually have a 3-pin noisemagic NMT-2 thermistor device here, and I experimented with using that on the card, but where do I put it?? It needs to be near a heat source on the card so it detects the temp changes and ramps the 3-pin voltages appropriately. It sorta worked when mounted near the voltage regulation stuff on the power connector, but not all that well. Just too many wires and ghetto mounting for a not-so-great result.

I am using a DFI LanParty NF4 SLI-DR motherboard which has two temperature controlled motherboard 3-pin headers, but they're both in use. Then it hit me: why not use a 3-pin splitter on the CPU fan header, and feed both the CPU fan and the VF-700cu fan from the splitter? Tying the VF-700cu fan RPMs to CPU temps should work perfectly! And it does. The CPU fan and the VF-700cu fan ramp together now.

The DFI bios has temp range settings for two fan headers, in fact. One based on CPU temps (what I am using), and the other based on "PWM temp" which I assume is the power regulation circuitry. There is a third temp range but it's dedicated to the low-profile northbridge fan which sits DIRECTLY under the first video card slot..

Anyway, this seems safe to me.. I can't think of ANY time the video card is under load and the CPU isn't also under load.. can you guys? It's worked like a charm so far, and it beats the crap out of a constant speed fanmate solution.. CPU gets hot, fans speed up.

In a perfect world I'd figure out some way to make the 4-pin PWM header work with the Zalman 3-pin connector, so the GPU temps controlled the fan instead of the CPU temps. But for now, this simple solution is working great!

* and boy does my wallet hurt! But greater than 6800 ultra SLI performance in bf2 sure is nice..

clarkkent333 · Post by **clarkkent333** » Wed Jul 06, 2005 10:01 pm

Why not just get a rheobus and turn the knob when your start a game. When its done, turn it back down. Easy peazy.

wumpus · Post by **wumpus** » Wed Jul 06, 2005 11:07 pm

Yes.. and maybe I should get a calculator to add up numbers too.. or better yet, an abacus!

Tzupy · Post by **Tzupy** » Sun Jul 10, 2005 2:00 pm

Probably the safest solution would be to get a 4-pin PWM fan and replace the Zalman VF-700 Cu's original fan. Searching the forums for '4-pin PWM fan' I found a thread on this topic. It seems that JMC makes such fans, but they are high speed and noisy. Another source is the Prescott boxed cooler, with a Sanyo Denki 4-pin PWM fan. However, when replacing the fan of the VF-700 with this kind of PWM fan, it would be wise to have a case fan blowing at the VF-700, just in case it won't work properly and you want to protect your 7800 GTX from overheating.

wumpus · Post by **wumpus** » Sun Jul 10, 2005 9:44 pm

Well, the only downsidesto this approach are

1) it requires a mobo that has thermally controlled 3-pin fan headers
2) it scales the GPU fan with CPU load

I believe most decent modern motherboards should have temperature controlled fan headers. I certainly hope this becomes a standard feature in most mobos, because it's a great "out of the box" solution to controlling fan noise.

The GPU/CPU scaling is a problem if you do a lot of cpu-only intensive tasks, such as video encoding. In that case the GPU fan will spin up unncessarily, because it's blindly tied to CPU temps.

I don't mind too much because I don't tend to do a lot of long-running CPU intensive tasks. I'll encode video occasionally but not enough for it to be an ongoing problem. It's a side effect I am OK with for now.

That said, if one could locate a 4-pin PWM fan and retrofit it on the Zalman, that'd be the best solution, no doubt about it..

MrMajestic · Post by **MrMajestic** » Wed Jul 13, 2005 12:38 pm

Maybe this will work?

http://www.adpmods.com/case-modding/ARX ... -1705.html

_xhp_ · Post by **_xhp_** » Sun Jul 24, 2005 12:49 pm

The better way would be to connect the fan to the 3-pin fan headers on the mobo, but use speedfan to control the speed of the GPU fan depending only on temperature of the gpu and gpu ambient (and not depending on the temperature of the CPU). There are three controlable headers on the lanparty so it should be enough...

scotty6435 · Post by **scotty6435** » Sun Jul 24, 2005 2:54 pm

^^ agreed. I've done this on mine (with a modded nexus fan instead of the slim zalman) and it runs at 1% idle with an underclocked 2D mode and 4% at full load. Temps never exceed 55 degrees load and 45 degrees idle.

addyngan · Post by **addyngan** » Wed Jul 27, 2005 6:44 am

How do u configure speedfan to read the GPU temperature?

bsix · Post by **bsix** » Thu Jul 28, 2005 11:27 am

I am interested in this as well. If you connect to the motherboard - as was pointed out before , you control on CPU temp or PS temp. So if you split the CPU header and used speedfan you could be controlling the GPU and the CPU off of GPU temp! I'm sure that's not the intention of the post. I assume you meant connect to the PS header and use tha?

If the other two fan connections (#4&#5) can be controlled by speedfan that would be great - would really help since I have 5 fans in the system, front case, back case, power supply, CPU, GPU and northbridge.

Thanks

bsix · Post by **bsix** » Thu Jul 28, 2005 11:43 am

I am interested in this as well. If you connect to the motherboard - as was pointed out before , you control on CPU temp or PS temp. So if you split the CPU header and used speedfan you could be controlling the GPU and the CPU off of GPU temp! I'm sure that's not the intention of the post. I assume you meant connect to the PS header and use tha?

If the other two fan connections (#4&#5) can be controlled by speedfan that would be great - would really help since I have 5 fans in the system, front case, back case, power supply, CPU, GPU and northbridge.

Thanks

toNka · Post by **toNka** » Fri Jul 29, 2005 1:11 am

Maybe this is a dumb question but...
Can't you just plug the Zalman fan into the gfx card.
Just make an adaptor right...?
The PWM should be able to control the fan speed of the Zalman, right?
If my assumption is correct, the header on the X800XT is this:
Red = 12v, Black = Ground.
Get a 4pin -> 2pin adaptor and just make sure the 12v and ground are going to the right header.

toNka · Post by **toNka** » Fri Jul 29, 2005 1:13 am

***Double Post***

***Mods, Please Remove***

toNka · Post by **toNka** » Tue Aug 02, 2005 10:59 am

Can anyone verify if the 4pin --> 2pin works with PWM?

_xhp_ · Post by **_xhp_** » Tue Aug 02, 2005 3:45 pm

bsix wrote:I am interested in this as well. If you connect to the motherboard - as was pointed out before , you control on CPU temp or PS temp. So if you split the CPU header and used speedfan you could be controlling the GPU and the CPU off of GPU temp! I'm sure that's not the intention of the post. I assume you meant connect to the PS header and use tha?
Thanks

His (and mine) dfi Lanparty has 3 controlable headers on it. One for the CPU, one for the chipset, and another one. The best way to connect the gpu fan would be to attach it to the third header and control it only depending on the gpu temp...

If he is a true silence freak he replaced that chipset screamer with something passive and has a extra fan connector free on the mobo...

Controling CPU fan based on the GPU temp only is not advisable...
But, with speedfan you could control the mobo header based on the GPU AND CPU temperatures (the only problem with this is that you double the noise when only CPU OR the GPU is hot, but not both. Nevertheless, on idle both will be cold and silent)...

Thermally controlling a Zalman VF-700cu

Thermally controlling a Zalman VF-700cu

Speedfan

Speedfan

Re: Speedfan