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PCI Slot Voltages

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dbranger

Junior Member
I am trying to design a simple PCI slot fan card. Basically the board will fit in a standard 5V PCI slot and be able to support a single fan (80mm?) connected to one of three fan headers.

My question is whether or not the +12V, +5V and +3.3V are already active in the PCI slot? In other words, do I have to activate the slot using TDO/TDI and/or the /PRSNT1 and /PRSNT2 pins or even some other method? Or can I simply make a card that lifts +12V from pin 2B and GND from 3A?

The way I have it designed on paper is:
TDO connected to TDI
/PRSNT1 connected to GND (and /PRSNT2 left open, to enable 25W operation)
+V I/O pins are decoupled to ground (.01uF per pin)
+3.3V pins connected together and used to power a 3.3V fan header (7.6A max)
+5V pins connected together and used to power a 5V fan header (5A max)
+12V connected to a 12V fan header (500mA max)

Is any of this possible?
 
+12V, +3.3V, and +5V are always there, and always on. Dont mess with V I/O. Dont mess with any signal lines.
 
You don't have to connect the JTAG lines for your fan (TDI & TDO... LOL)

Do you need to use all three rails? I doubt it. I'd just use the +5V rail and design a board with fans using that. Simple and effective.
 
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