I have 3 Vantec Stealth fans in my PC. As suggested, I used the 3-to-4-pin adapter to plug them, but I plugged them all on the same cable, thinking it would make no difference since a fan doesn't need much power, right ? Plus that way, the fan cables weren't taking much space. So I started having problems, my cdrom would freeze, I wasn't able to install my board drivers, sometimes I couldn't boot from the cd, as the BIOS would simply bypass the boot sequence, and boot straight from the hdd. I then decided to dedicate one cable for each fan, and problems were solved ! So fans DO need power, maybe not much, but it needs it anyway, so plugging your 3 fans, hdd and cdrom on one single cable is a bad idea. I'm not sure if it'd work with a bigger psu, but I know it doesn't work on mine, and it's not a cheap one. C'était à titre d'info. Sorry I was just letting you guys know about the experience I just had.
Well they use the 12V rail. What else uses it ? Is the "P4" connector of the psu on the 12V rail ? If so, that may be the cause of my previous problems since the FRN2 uses this connector, unlike other boards (the DRV5 wasn't using it). Also, something that I find odd, is that the 80mm version (the ones I have) are the most power-hungry of that line of fans (60mm, 80, 92 and 120). I would have thought that either the 60mm or the 120mm would be the most power-hungry fan. Do you recommend using only the 3 pin connector ? I'd use less cables and I would also be able to use my board's sensors. I've read quite many times that it's not a very good idea.
I've just read that the CPU can be powered off either the 12V or 5V rail. I'm not sure what to think. I'd play around with the fan headers on the motherboard and see if you can get a workable combination with the fans going.