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Dual power supply mosfet mod???

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FunkDaMonkMan

Member
Joined
Dec 31, 2001
I have a Biostar M7NCG-400 mobo running in my car and I have a dc-dc powersupply powering it. (The mobo is NF2)

When the car is on, everything is fine because the voltage into the powersupply is 14.5V, and that makes it put out 11.98V on the 12V rail. Perfect!

When I turn the car off, the voltage in to the powersupply is 12.6V, and so the output voltage on the 12V rail is something like 10.85V. The other voltages look just fine. Needless to say... I can only get my machine to run on that if I underclock it to a 100mhz bus (I'm on a 166mhz bus right now).

I have a 12V line regulator that is normally used to power dc-dc power supplies that require STRICT 12V. I accidentally bought it b/c i thought mine did, but obviously mine needs as much as it can get. This got me thinking.

If this puts out a perfect 12V, could I run a wire from this to the mosfets, just like some of the voltage mods I've seen here. Is there going to be a problem with my motherboard getting 10.8V through the atx connector, and then 12V at the mosfets? Thanks for your help.
 
I would advise agaisnt it. Reason is, both of those lines are connected to a single ground and one of the sources might get burned if you do what you are describing. I would put a switch on the powersupply thats connected to ATX connector so it would shut off when the car does.

Of course the ultimate powersupply would be the one that works from 12V and powers the whole computer.
 
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