The book on my Maximus Formula motherboard tells me "If installing a dual-core CPU, connect the chassis fan cable to the CHA_FAN1 connector to ensure system stability". Now the chassis fan cable is the CPU fan right? And if so why can I not plug it in the CPU_FAN? Has anyone experienced this problem???

The chasis fan connector is located by the PCIEX_1 slot. I connected by main chasis exhaust fan to this and the CPU to it's labeled connector. Any additional chasis fans can be connected in any of the other connectors located thoughout the board.

Yes, but do you have a Core 2 Duo installed?

mainer-in-exile input is correct... I have the same board as you do. The fan connector selection is not a function of CPU type.

There's no problem. Chassis = Case

Plug the CPU Fan into the CPU Fan Connector
Plug the Case Fan(s) into the Chassis Fan Connector(s)

If the BIOS detects high MoBo temperatures, it's gonna signal CHA-FAN1 to speed up. If you don't connect it, it won't be able to respond.

http://dlsvr01.asus.com/pub/ASUS/m [...] ormula.pdf

Look at page 2-5

You will see that the connector for the CPU Fan is located at the upper right of the image "north" of the memory slots and adjacent to the normal/high/crazy LED's

Thermal sensor connections are covered on page 2-32
Fan connections are covered on page 2-33

Read more on the BIOS functions associated with these fans on 4-31 thru 34. Saee Also 5-31 for how Q-Fan works.

So when it says "If installing a dual-core CPU, connect the chassis fan cable to the CHA_FAN1 connector to ensure system stability" on page 2-8 it basically means dont plug the case fan into the CPU fan connector? (If so that is kind of obvious)

I think what is saying is:

a) make sure you do plug it in
b) make sure you plug it in in the place where it's going to do the most good.

I didn't read the whole manual to get an understanding of how all the fan stuff works but realize that all these fans give feedback to the BIOS vis the on board temp sensors or the thermal sensors provided with the MoBo. Seems the BIOS has "hard wired" CHA-FAN 1 to be the main chassis fan which when the BIOS receives a signal saying MoBo sensor is too hot, it's gonna speed up that fan.

I don't recall the manual to well from last Friday but my guess is it wants:

CHA_FAN 1, CHA_FAN 3, CHA_FAN are all controlled by "built in" sensors that are gonna speed up these fans is it senses hi case temps.

OPT_FAN1, OPT_FAN2, OPT_FAN3, my guess is works with the thermal sensors provided so maybe you sticking them on vid cards and HD and should place the fans / connections accordingly.

The PWR-FAN my guess is an auxillary power supply fan connector.