Fan speed during POST

  • Thread starter Thread starter Kiran Kumar Kamineni
  • Start date Start date
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Kiran Kumar Kamineni

Has anybody seen the following effect?

When the system boots up, the fan speed of my BFG 6800 OC is high and it
slows down when windows boots up and I get the Login screen (noticable with
the sudden decrease in noise).

Whats causing this sudden slow down??
 
Has anybody seen the following effect?

When the system boots up, the fan speed of my BFG 6800 OC is high and it
slows down when windows boots up and I get the Login screen (noticable with
the sudden decrease in noise).

Whats causing this sudden slow down??
Click to expand...

I get that too.

I always assumed it was a power supply sag caused by the vid card
going into "performance" mode. It seems as if *all* of my fans slow
down once the vid card starts pulling extra juice, but maybe it is
just the vid card fan... hard to tell with fan noise. It happens as
soon as the GUI appears on boot. At first I thought it was a power
supply problem, but it happens with two different high-quality power
supplies.

My vid card (eVGA 6800 GT) doesn't advertise any special fan control
capability, and there's no background software or service running that
would cause the slowdown of the fan. It slows down once the GUI
appears, and speeds up during the boot process. The fan speed never
changes during intense 3D activity. Only at boot.
 
Folk said:
I get that too.

I always assumed it was a power supply sag caused by the vid card
going into "performance" mode. It seems as if *all* of my fans slow
down once the vid card starts pulling extra juice, but maybe it is
just the vid card fan... hard to tell with fan noise. It happens as
soon as the GUI appears on boot. At first I thought it was a power
supply problem, but it happens with two different high-quality power
supplies.

My vid card (eVGA 6800 GT) doesn't advertise any special fan control
capability, and there's no background software or service running that
would cause the slowdown of the fan. It slows down once the GUI
appears, and speeds up during the boot process. The fan speed never
changes during intense 3D activity. Only at boot.
Click to expand...

Same here. I couldn't figure it out for a while as I had never heard it
before, but, I had a new power supply with a variable speed fan installed
whereas before it was a single speed fan. Immediately prior to the fan
slowing down I hear six clicks which I had thought was drive heads so
thought the sound of something slowing down was to do with a drive, but, a
mate told me the PS fan runs at full speed up to a certain point in the boot
sequence. I had never thought it was when the GUI appeared, learn something
every day.

Rob
 
Kiran said:
Has anybody seen the following effect?

When the system boots up, the fan speed of my BFG 6800 OC is high and it
slows down when windows boots up and I get the Login screen (noticable with
the sudden decrease in noise).

Whats causing this sudden slow down??
Click to expand...

Likely it defaults to high speed on bootup as a fail-safe but when the
driver loads it reduces the fan speed..
 
The fan speed is driver controlled therefore the fan runs at maximum speed
until the driver initialises and takes control.
 
The fan speed is driver controlled therefore the fan runs at maximum speed
until the driver initialises and takes control.
Click to expand...

If the fan speed is driver controlled, why doesn't the fan speed
change once the driver initializes? My 6800 GT *never* changes fan
speed once I've booted into the OS, no matter how much I punish it
during heavy 3D processing. There are only a few high-end cards that
advertise the capability to alter fan speed, and those are the ones
with those big-assed fans that take up two slots.

So why would it slow down when it boots to the OS and then stay that
way until you reboot, regardless of the onboard temps? Doesn't make
sense.
 
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