mobo boot w/o CPU fan

joker_927 · January 2nd, 2003, 01:53 AM

I have so many posts about my new setup (mostly fans) but I think I know exactly what I am getting.

They CPU fan I am buying is actually a case fan that will mount onto my Heatsink. Well, the case fan (seen here) uses a 4-pin connector to get power. My new motherboard, the Kt400 Soyo Dragon Ultra (in the manual) says it won't boot if no CPU fan is plugged into the CPUFAN 1 slot on the motherboard. Well if this fan uses a 4-pin connector stright to the PSU, and the mobo won't boot unless it detects a 3-pin fan connect, I think I'm going to have a problem.

I don't know how much power the mother board gives out in its little 3-pin thingy but, if I have to, I may cut the wires from the 4-pin and make it a 3-pin.

Whcihc brings up another question of what the motherboard considers a fan. This fan may not have an RPM detecter in it, so it doesn't even use 3 pins, just 2.

*sigh*

Well, any information you can give me on my paradox would be appreciated.

Thanks

Wizzard~Of~Ozz · January 2nd, 2003, 02:00 AM

The fan MUST have a rpm monitor pin, Can you replace the CPUfan? (not the sink, just the fan?) if not just plug a rear case fan into it, it just requires A fan. Also most of the time you can diasable this in the BIOS, but I'm not sure with that board.

OuTpaTienT · January 2nd, 2003, 02:04 AM

Yep. Should be able to turn off the check for cpu fan in the bios. I can with my Soyo Dragon Plus.

Peter M · January 2nd, 2003, 01:54 PM

Most boards will not even boot into BIOS setup when no spinning CPU fan is detected. Too risky.

dunbar · January 2nd, 2003, 02:27 PM

Just a side note for any late arrivals...

Fans themselves do not need to provide any RPM connection (to the outside world) in order for a fan to spin - it is not a requirement determined by the fan.

The Wizz-of-ozz meant that the mobo must have a fan RPM signal, otherwise no bootup will be allowed without the signal. Wizz is suggesting a test situation, not a long term solution, where the signal from some other fan will be usd to fool the BIOS into allowing system bootup.

Also: if the CPU heatsink is not cooled, in otherwords, if a fans airflow does not flow onto the CPU heatsink, the CPU can get toasted, so the real need here is to have A] a fan which has its airflow cooling the CPU heatsink, and B] also having a fan which is also telling the BIOS that it is spinning, doing so by an RPM signal which is telling the BIOS that there is a fan in the system.

Lastly, if you choose to separate the fan RPM signal from the fan which is actually providing CPU cooling airflow, assume that there are risks, and be responsible for any consequences.

I worry about the possibility for misinterpretations of the intentions here, wizz, nothing more.

OuTpaTienT · January 2nd, 2003, 03:08 PM

People aren't THAT dense are they? Ok nevermind that.

But it certainly CAN be long term solution if you know what you're doing. I had a fan on my video card connected to the motherboard's cpu fan connector for ages. This was done because my cpu fan had no rpm monitor and it connected straight to the ps. Worked great, for years.

joker_927 · January 2nd, 2003, 05:03 PM

That is what I will probably end up doing, thanks.

Wizzard~Of~Ozz · January 2nd, 2003, 05:15 PM

Quote:

Note: The following must be observed to secure the normal functioning of
“Fan-Off Control”:
1. FOC only works on CPUFAN 1.
2. CPU fan with sensor pins must be used.
3. CPU fans approved by AMD are strongly recommended.
The “HOT KEY” function is provided for the CPU fans without sensor pins, to
avoid the power off. Users may press the “Insert” key to jump over the “Power
Off” mode; go to the BIOS and disable “FOC”. Now system can be booted
normally.
We provide the following user-friendly protection features:
1. Fan-Off Control: The motherboard detects the status of the CPU fan and
protects the CPU by automatically disconnecting the power supply. The
default value of this function is Enable. After booting up, the user may
disable it.

There is the answer, it was in the manual, what a wierd place to hide it

page 16 actually

JayMan · January 2nd, 2003, 05:36 PM

hehe another case of RTFM.... hehe

JayMan

Arjay13 · January 2nd, 2003, 05:37 PM

Why don't you buy a proper cpu fan instead and save yourself the hassle? There are plenty of good ones out there.