Puzzler: Zalman unclocks 8800GT

[nhobo]

Here's one for the weird file:

I put a Zalman VF900cu on an eVGA 8800GT. It lowered the idle temp from 56 to 39 C. and runs much quieter than the stock fan at full blow. But with a 3-pin connector it can't plug into the fan port on the 8800GT, so it has to go into a fan header on the DS3L, which means the 8800GT can't control the fan. Works fine - or should I say runs flat out - off the mobo, but I can't figure out how to control the damn thing with Speedfan.

With Speedfan I can control the CPU fan but not the case or GPU fans. It shows the fan speed but the speed control has no effect. No problem - the Zalman came with a Fan Mate 2, Zalman's speed control device. So I plug that into the mobo, turn the speed down a bit from the somewhat whiney 2586 rpm reported by Speedfan. But on reboot the GT's overclock is lost?!

So I tried the Fan Mate in a different mobo header, to no avail. Then I ran it off a molex with the same result - the OC disappears on rebooting. Using RivaTuner for the OC, which works fine except when I use the stinking Fan Mate.

Eternal gratitude and good karma to anyone who can show me how to make Speedfan control the Zalman. But what I'm really interested in is why the Fan Mate knocks out the OC. Kudos and a Gold Star to anyone who can figure this out.

 

[nhobo]

OK, looks like the fan headers on the DS3 series are fixed to run at 100%. Guess I'll try the old 7v fan hack ...

 

[nhobo]

7v fan mod done, don't know the RPM because Speedfan can't read it off the molex, but considerably quieter with max temp 54 C. under 3x Real-time HDR IBL.

Conclusions -> The 3-pin Zalman VF900cu doesn't plug into the 4-pin video card fan header, the DS3L doesn't allow voltage modualtion of fan headers other than the CPU, and the Fan Mate 2 causes unsolvable problems with overclocking.

 

[nhobo]

GPU locked up under load - I guess 7v isn't enough. Back to square one.

 

[nhobo]

OK, strapped a small quiet Scythe to the VF900cu heatsink. It ain't pretty but it's quiet and cool. Fewer, larger fan blades, 1300 rpm (vs. 2600 on the Zalman fan). Max temps so far (under GT Legends) 46 C.