Hyperthreaded CPU makes a noise!

RedDom · Post by **RedDom** » Sat Oct 09, 2004 10:17 am

If I run two instances of Prime95 on my P4 2.8 one on each virtual cpu using hyperthreading, I can actually hear the cpu! I thought it would be silent, but it makes an extremely faint chirping or high speed switching sort of noise.
The PC is a hush -ATX with a soft mounted 40GB samsung laptop drive which to all intents and purposes is completely silent.
If I run two instances of prime 95 I can hear this noise, at first i thought it might be some noise from the heatpipe or coil buzzing, but as soon as i stop one instance the noise stops, but the temperature remains mch the same.
It just goes to show that no matter what you silence, there will always be something else to make quieter.

RD

Post by **Ralf Hutter** » Sat Oct 09, 2004 12:43 pm

I've heard this noise from many, many P4 CPU's, but only when they're under full load. Pre-HT P4's did this as well. Most people probably never hear it because their base system noise is too loud.

luminous · Post by **luminous** » Sat Oct 09, 2004 2:53 pm

Ohhh my.... you sure do learn something every day. I would never have thought that a CPU would make noise. Just goes to show that there really is no end to our silencing game.

lenny · Post by **lenny** » Sat Oct 09, 2004 4:46 pm

luminous wrote:Ohhh my.... you sure do learn something every day. I would never have thought that a CPU would make noise. Just goes to show that there really is no end to our silencing game.

Oh yes, there is. With advanced age comes hearing loss

By the way, there are some who suggested in the past that the sound may be due to coil / inductor whine from the power regulation circuits on the motherboard. Sounds more plausible than the CPU itself making noise. But since I haven't heard it for myself I'll keep an open mind about it.

mathias · Post by **mathias** » Sat Oct 09, 2004 4:51 pm

lenny wrote: By the way, there are some who suggested in the past that the sound may be due to coil / inductor whine from the power regulation circuits on the motherboard. Sounds more plausible than the CPU itself making noise. But since I haven't heard it for myself I'll keep an open mind about it.

Maybe heatsinks on the mosfets might get rid of it?

Edward Ng · Post by **Edward Ng** » Sat Oct 09, 2004 7:14 pm

The heatsinks on the MOSFETs won't do it; I installed Microcool MOSFET ChipSinks on my heavily overclocked K7 rig and they did nothing for the coil whine during load (although they did cut down on PWM temps by a good ~25C).

My P4 machine also emits remarkably loud whine under Prime95; there's not much you can really do about it. I know someone who managed to cut down the whine by applying some sort of silicone/goop/stuff onto his coils. He says it works and doesn't cause any heat issues, but it's hard for me to reach him because his machine has been bit by some sort of crazy glitch, and he's all the way out in the Czech Republic.

I think it's the fact that he ran his poor CPU at ~70C all day, but that's just me.

If anyone wants to know what he used, his SPCR handle is trodas.

-Ed

mathias · Post by **mathias** » Sat Oct 09, 2004 7:29 pm

Maybe some sort of electrical equipment expert would have some ideas as to what can be done about that, any idea if coils can be replaced like capacitators?

canthearyou · Post by **canthearyou** » Sun Oct 10, 2004 8:36 am

I had a stereo amp once that when you turned the volume all the way up with the speakers cut out you could plainly hear music from the MOSFET amps.

Straker · Post by **Straker** » Sun Oct 10, 2004 2:11 pm

hmm, coils always make noise, MOSFETs shouldn't make much/any though, weird. inductors basically do the same thing capacitors do (wrt DC power regulation), but with current instead of voltage... if you could obtain approximately the same gauge wire and an iron ring about the same size you could just wind new ones yourself. depending on exactly what they're regulating the power for you may be able to replace specific ones with capacitors too, but that probably wouldn't be a hot idea if whoever designed the mb had any idea what they were doing.

best idea would probably be to just try hot glue/silicone.

also see http://www.ibiblio.org/obp/electricCirc ... DC_15.html , free textbook

josephclemente · Post by **josephclemente** » Sun Oct 10, 2004 5:41 pm

On SFFTech someone used earplugs inside his coils and reported that it worked well.

See:
http://forums.sudhian.com/messageview.a ... adid=66029

halcyon · Post by **halcyon** » Sun Oct 10, 2004 11:08 pm

That's a great tip. I wonder how high temps those earplugs can tolerate? Sometimes those coils can get pretty hot.

silvervarg · Post by **silvervarg** » Mon Oct 11, 2004 1:52 am

What a great tip to put earplugs in the coils!
A much neater solution than gluing them.
The noise comes from the winding in the coils moving due to the magnetic forces the coils produce, so by doing anything that fixes or damps the movement of the windings it should reduce sound a lot.

I guess it will vary quite a bit with different kinds of earplugs, but I have never seen motherboard coils that go much above 50C, so I think most earplugs should work fine.
Before you try I would check that the specific earplug really can take the heat. E.g. put it next to your CPU heatsink base or something else that is at least 50C hot.
Also check that the earplug does not conduct electricity. I would be very suprised if it did, but I would still check.
Sometimes the coils are placed very close to the MOSFET, and they can become very hot.