Underclocking, is it worth it?

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lightforce
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Underclocking, is it worth it?

Post by lightforce » Wed Jan 21, 2004 6:06 am

im gonna get a amd 2500+, compucase, probably nexus 3000 psu. but the asus motherboard (with inbuilt graphics) doesnt undervolt.
would it be wise for me to get a motherboard that does?
problem is there's not a lot of motherboards with inbuilt vga graphics available.

the main reason i go for the asus is that there's no fan on it.

would i be better off with another motherboard WITH a fan but undervoltable ?

my system:

amd 2500+ should run pretty quiet with that zelman (sp?) 7000-fan whatever.
samsung p80 drive.
silent compucase
nexus 3000 OR possibly SS-300FT from seasonic.
no extra graphiccard. no heavy load work expected.

whole system expected to have ONE fan (on the cpu)

what do you think will be the noisiest part? the psu should be around 20db with normal work from what i understand.

is underclocking/undervolting something for me here?

Lifecycle
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Post by Lifecycle » Wed Jan 21, 2004 6:24 am

The advantages of underclocking and undervolting are that your CPU will produce less heat and so will be easier to cool, therefore allowing it to be cooled with a slower speed fan, hence producing less noise.

The amount of heat a CPU kicks out is dependent on both the speed of the chip and the voltage. Lowering one reduces heat, lowering both reduces heat further still.

Underclocking will obviously mean that you lose performance. How much you need that CPU performance is up to you, but chances are you can swallow anywhere from a 10% to a 50% drop in processor speed without noticing an actual drop in real-world use. Games etc. are often much more dependent on graphics cards than CPU's, and provided you keep over 60fps (or whatever), everything will be sweet. Other apps can be more sensitive to CPU speed, so it does very much depend on what you're doing.

Undervolting has similar issues to overvolting, in that you need to test your CPU for stability at reduced voltage. Like overclocking and overvolting, the limits of the CPU are quite wide and varied, even within the same batch and processor type.

The main advantage of having an undervoltable motherboard is that if you do decide you want to drop noise further, you have the option to do so, by cutting the amount of heat your processor puts out (along with also underclocking, which most/all modern motherboards can do anyway).

I'm sure someone else can give a better answer than me. You may also like to have a search through the forums too.

HTH.

lightforce
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Post by lightforce » Wed Jan 21, 2004 6:52 am

ok but let's say i buy a Zalman 7000/A Cu / AlCu to cool my amd 2500+.

the info i got about it is:

Noise: 20 dB at 1.350 rpm, 25 dB at 2.400 rpm

so let' say i get it to run at 20db, then the question is if undervolting would make much difference

trodas
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Post by trodas » Wed Jan 21, 2004 7:50 am

My friend wanted a noiseless server. It still has to have decent power, so he bought a Duron 1.4Ghz (this is enough fast :wink: ) and underclock it to 1.2Ghz - and under voltaged it as well, from 1.4Vcore to 1.2 :wink:
As result, he was able to cool it pasively with Zalman CNPS3100-Plus (the same one as im used to made a passive-only machine with 1.2Ghz VIA C3, check there http://forums.silentpcreview.com/viewtopic.php?t=9704 ) heatsink, however when it show 85 degrees on full load, he installed there a fan again - at 5V instead of 12V, but still - fan :?
So, its worth, but not that much :roll:

ruprag
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Post by ruprag » Wed Jan 21, 2004 8:02 am

Well I run my 2000xp chip at 0.1v lower voltage than it is rated for but at the same speed => drop in heat but no performance loss => yes get a mobo that undervolts, you can always put a zalman on the northbridge (I did :-))

Harry Azol
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Post by Harry Azol » Wed Jan 21, 2004 9:35 am

I would say don't bother..

even @ the slowest/quietest speed (5v) the zalman 7000 will be cooling your cpu very well..

Trip
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Post by Trip » Wed Jan 21, 2004 10:11 am

be sure and look at the thermalright heatsinks as well :wink:

ZM-NB47J may not be compatible with all mobos and may not be enough to cool all North Bridges. Someone can verify the later comment.

lightforce
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Post by lightforce » Wed Jan 21, 2004 10:52 am

on one of the motherboards im looking at, there's no fan at the northbridge, does that mean it doesnt need one?

GamingGod
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Post by GamingGod » Wed Jan 21, 2004 11:01 am

If it doesnt have a fan on the northbridge then it doesnt need one. Alot of people remove the fans from their northbridges anyways.

Startled Pancake
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Post by Startled Pancake » Thu Jan 22, 2004 2:28 am

From what Ive read underclocking does very little to reduce heat output, its all about voltage really. Try:

http://www.cpuheat.wz.cz/html/AXP_multi ... iplier.htm

This might allow you to soft change the voltage in windows. Then again it may cause you PC to explode which will Im sure for a brief moment make your life much more exciting.

lucienrau
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Post by lucienrau » Thu Jan 22, 2004 5:25 am

Underclocking has not made a great difference for me, however, undervolting makes a HUGE difference in temparature, even as little as .1v creates lower temps. I usually try for a slight overclock on the FSB while reducing the voltage a little.

je_zza
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Post by je_zza » Thu Jan 22, 2004 7:05 am

I have a PIII 800EB that is undervolted from 1.65 to 1.4V and is perfectly stable for 9 months, 35C idle and 48C load. I'm using the stock intel HSF but at 5V and it is very quiet. Underclocked and 5V this equates to a 10C drop in temperature compared to stock vcore and 5V. Undervolting is fantastic.

CeeJay
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Post by CeeJay » Sat Jan 24, 2004 2:48 am

8rdavcore is capable of undervolting at least a Asus A7N8X , maybe It will work too on the MB you've choosen

http://www.hasw.net/8rdavcore/index.html

And undervolting does work , but even without your choice of component will ensure you a very cool and low-noise system.

I myself am using a custom mounted Zalman CNPS7000 (It won't fit on a Abit NF7-S 2.0 normally - especially since this isn't the A version) with a Seasonic SS-300FT (The Nexus3000 might be better .. I'm using this because I was one of the lucky winners that got a prize in a contest a while back here on SilentPCreview)

The Noisest part in my computer depends on what kind of load i'm having.
If the DVD/CDRW drive is spinning it takes first prize - but running idle I'd say that it's probably the monitor hum thats the most annoying - I can hear the PSU buts its very lownoise and its not an annoying sound.

I use Speedfan to control the fan speed.
On my system it makes the fan run it's bare minimum speed where I can't hear it (2% setting in speedfan) almost all the time.
Only something like folding@home can force it up to 20% - it never runs full speed.

FrankT
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Post by FrankT » Sat Jan 24, 2004 3:44 am

Startled Pancake wrote:From what Ive read underclocking does very little to reduce heat output, its all about voltage really.
That is true, and from my experience I found that by underclocking more I could then undervolt more as well. It depends how far and slow you want to go.

I would recommend an undervoltable motherboard because you have the choice of trying it out. If it doesn't work then you can crank it up to full speed again.

FrankT
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Post by FrankT » Sat Jan 24, 2004 3:52 am

GamingGod wrote:If it doesnt have a fan on the northbridge then it doesnt need one. Alot of people remove the fans from their northbridges anyways.
My experience has been that by removing the cpu fan on my machine (orginally with a zalman 6500AlCu and 92mm fan on lowest (<5v) speed, replaced with an NCU-1000), the northbridge heatsink became almost too hot to touch. I had to fit a bigger heatsink. It is something to keep in mind if you are going for minimum airflow and hopefully minimum noise :)

trodas
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Post by trodas » Sat Jan 24, 2004 6:10 am

Its all matter of BIG and huge cooper heatsinks 8)
Don't let get ripped by the Al crap, just buy big and huge Zalmans and you can get the machine working even passively cooler - attaching the heatsink to case as i did by heatpipes also drasticaly crank down the temperature - however it also heat-up the whole case a bit :wink:

So at ens, its all matter of exchanging higher temps, witch don't hurt a thing (mine CPU is over 50 degrees on iddle and what? Friend Athlon is over 60 at iddle all the time for 4 years and what?) in sake of quiet operation. Airflow in case is ofcourse key. It can be, however, archived even passively, no fan need.

See how i did it:
http://trodas.mujhost.cz/galerie.php?p= ... 7&d=1&v=v2

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