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Thread ID: 50401 2004-10-19 10:42:00 Strange: CPU fan changes in pitch when mouse button held down george12 (7) Press F1
Post ID Timestamp Content User
282696 2004-10-20 06:59:00 Well, I have deduced that it is the Graphics Card.

Whenever I do anything graphical or involving redraws of the screen ie. scrolling, the cpu fan lowers in RPM until the ... thing ... is complete (ie. the 1/2 second scroll movement has finished).

Now WHY the hell could this be happening?

My Graphics card is an integrated SiS 661FX card running at 166MHZ, sharing 64MB or DDR400 memory.

It happens at all refresh rates, resolutions, and colour depths.

There is no fan on the SiS chip, so it can't be that when the GFX get going the SiS fan spins up and the CPU fan therefore has less power.

I have a good brand of 300W powers supply (Auriga). I only say they are good because in my experience they have all run well and never failed. I have one 5400RPM hard drive, a DVD-ROM drive, floppy drive, and that's it running off the PSU.

I'm pretty sure it's not a power issue because when I do something like put a disc in the DVD drive and let it spin up, there is no change in fan RPM.

So, we know WHAT is causing it. Can anybody tell me HOW/WHY?

Cheers
george12 (7)
282697 2005-04-28 07:11:00 Now this may seem a really late post, but I've solved the issue and can't resist posting about it.

It IS power, and it IS CPU load.

When I scroll in FF it's fine. But when I scroll on a long page in IE, which I used back then, the CPU usage went to 100%, drawing too much power on the 12V rail for my CRAP psu to handle, and (now I've checked with a multimeter) drops the 12V rail into the 11's. Solution: Decent PSU. Although it's not much of a problem, so I won't bother. At least the thing's reliable.

Cheers George
george12 (7)
282698 2005-04-28 07:58:00 It seems not to have an IRQ. Also, it is only in certain programs etc.
It will have - it won't necessarily be under a heading FAN. If your BIOS has it you could turn off the throttle fan speed setting.
pctek (84)
282699 2005-04-29 07:34:00 It's not the FAN itself, it's just that the whole 12v rail drops under CPU load. george12 (7)
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