Underclocking for reduced heat

[Micah]

I'm thinking of putting together a MythTV box using components from my PC when I do my next upgrade. I have an Athlon XP 1600+ Since I'll probably be doing hardware encoding, I won't need a lot of CPU power. However, I would like to keep it as quiet as possible and am thinking about passive cooling.

How would I go about underclocking, and how significant would the difference be? Will I need a special heatsink, or can I simply remove the fan from my current heatsink (a Thermaltake Silent Boost)? Is this a crazy, stupid idea?

Any thoughts would be appreciated

Micah

 

[JBT]

it "may" work if you can undervolt it enough. which you would do in the bios or possibly a pin mod.

 

[Falloutboy]

you could but I don't think you could get the chip down to a low enough voltage and still have enough pwoer to run your myth box. you best be is to get a 35watt 2400 mobile and run it at 1.2ghz at something like 1.1 or 1.2v this would put it right around 15-20w output

 

[Zap]

I'd recommend AGAINST passive cooling. You can probably undervolt a quiet fan like the Panaflo 12L and have silence (outside the case) while still having about 10X the cooling of a passive setup.

 

[Micah]

Any suggestions on how to undervolt the fan? Can it be done in the BIOS? Or, do I need to buy a resistor-thingy that allows me to dial up and down the fan speed?

 

[JBT]

you can just swap the power on the molex connectors to undervolt the fan to 7v or 5v RED + black = 12

Yellow + black = 5v
yellow + red = 7v

iirc... anyways it may be swapped for 5 and 7

 

[InlineFive]

I have done an excellent with underclocking my Barton 2500+, mainly since I am an Almost Silent PC Nutjob. I undervolted the processor to 1.325v from 1.65v and my temps have gone down from 50c load with 12v fan to about 41c under load with 7v fan. Only thing is since I am betting you are using a Palmino those don't do well at all with any modification like this.

Your best bet is a Mobile Barton or a low-speed 256Kb Athlon.

 

[Zap]

If you do intend to keep that CPU, then just underclock it, undervolt it (if possible) and get a large heatsink that uses an 80mm fan. Depending on your noise tolerance you may be able to get away with a Thermaltake Silent Boost, or get a Thermalright SLK-900A (on sale now for $20 at SVC.com) and a quiet fan. Most people probably wouldn't be able to hear a quiet fan like the Panaflo 12L once it is inside a case, but again depends on your noise tolerance. Some no-noise nuts can't even tolerate imagined noise, LOL. (now to duck and hide, and wait for the flames to die down)

 

[Micah]

Well, I have a pretty good tolerance for noise, but this is for an HTPC-type box that will be sitting in the living room. I am trying to tackle the noise problem up-front instead of trying to reduce noise later.

I think undervolting the CPU and the fan is a good idea and I might give that a try. Right now, with the CPU at full speed I get around 50C core temp under load. To me, anything under 60C is acceptable. So, an undervolt plus a slow fan will probably keep temps inside the acceptable range.

 

[HeroOfPellinor]

Epox NF2 board undervolt to something ridiculous like 1.1 or something...that's the board you're gonna want to try this with. At that voltage with a 35W Mobile XP, an L1A at 5V would probably be more than sufficient for running the computer all the time.

 

[Jeff7181]

You could also consider modifying the design of the case. Take some pieces of poster board and masking tape and make a "tunnel" to route cool air from the front to the CPU fan, then make another "tunnel" to route hot air out the rear.

 

[Pathogen03]

Sounds sort of like BTX that the AMD nutjobs are all against.

 

[JBT]

Originally posted by: Pathogen03
Sounds sort of like BTX that the AMD nutjobs are all against.

ahah yeah right? I don't mind BTX at all if it is going to keep heat down then it should help everyone ones OC even AMD folks.. I buy new cases all the time. Infact I have switched about every component in the my system almost 4 times in the last three years. I don't see what the big deal is about switching stuff around if it improves on an aging standard.