So this is the second time this has happened. I was going to post about it the first time but completely forgot about it. It was a couple months back. I shut down my PC shortly after closing a game. And right as it shuts off the fan speed on my 960 shoots up for a brief moment before shutting down.
My first thought was: A feature to let out any excess heat because the system is being shut down so soon after GPU has been working under load? That’s the first thing that comes to mind. Could it be a power issue? I HOPE NOT. Never had any power issues. Other than my system turning itself on but that was a motherboard setting…
If it’s a feature, it should repeat under the same conditions. I’ve owned some cards (MSI) I think that did something like this, but I think it was intended to flush dust off the fans/heatsink and did it on start up.
I might be something as simple as the PWM signal shutting off slightly before the power shuts off. Like if you plug a 4-pin fan onto a 3-pin header it will spin at full speed because all it is receiving is 12V, no PWM signal to control it.
I’d say this is what it is, you want the default action of the fan to be powered on so it makes sense that during boot or shutdown when the speed control is off the fan will just run flat out for a moment. It’s definitely not a power problem.
Do a scientific test: the next time when you shut off your PC make sure to let it dissipate all the heat and see if it does this thing.
My PC only ramps the fans connected to the motherboard for a moment when it powers on and I think it’s because the system “tests” all of them and spits out an error if something’s not working. The GPU has it’s own BIOS so it’s fan curve and behaviour is indipendent from the rest of the system (if you don’t mess with it within and OS).
My GFs PC does this, on boot though. When it’s booting her card turns on the fan at full speed then slows down, sounds like a vacuum cleaner. My guess is as @w.meri suggested that the PWM signal isn’t there at boot (or in your case lost prematurely).
What model is the card? EVGA too? My GFs is a Gigabyte card I believe.
I’ve got a 4GB 960 ACX 3.0. The highest clocked one. Basically the top end 960 you can get from EVGA. As far as temperatures go… this thing scares the shit out of me sometimes. I dont know how it runs this cool. Nvidia showed a chart showing how the 960 is an “overclocker’s dream” and boasting about how power efficient Maxwell is. The thing runs at load under some of the most graphics intensive games at 50, 51 degrees. Fans are off the majority of the time. But that isn’t even the good part. That chart Nvidia showed, showed the core clock going up to 1.4GHz in the most extreme scenario. This fucking thing is sitting in my case, with fans basically off going up to to a point between 1.5-1.6GHz. And still has that same rock-steady temperature.
Talk about having “luck” with a CPU or GPU when overclocking. But holy shit. And i didn’t even touch it myself. I opened up Precision X once to see what goes on during load like that and that’s what i found. Maybe because it’s in such a massive case? Funny, because i played around with the fan controller in my Phantom 820 A LOT to try and get the best air flow. Perhaps that has something to do with it. I have a massive desk, too. And i felt bad about putting the Phantom on a shitty, dusty carpet. It’s on top of my clean desk, too. The dust filters, remove them periodically to check what they look like. But i haven’t cleaned them once since i built this system. No need.
I’ve had boards (I dunno if it’s just an Intel or BIOS-specific thing) that will spin a fan at full speed briefly when it measures 0 RPM. Having done 0 research on it, it’s probably because some of Intel’s stock coolers can’t start from a complete stop on the lowest speed.
Since they’re using a PWM signal to modulate the fan speed the voltage is a constant 12V so the fan can start with no issue at the lowest setting possible. Anyway this is OT so I won’t change the direction of this topic.
Actually no, I saw it with my own eyes. The low-end Intel coolers (e.g. the ones that come with the Pentiums) rock back and forth and then run at full speed. Other coolers don’t do that.
The voltage received has nothing to do with it if the current fan speed isn’t enough to push it over the first ‘bump’.
