If you Under Volt and Under clock a CPU, can you run it safely without a fan?

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Ready

Golden Member
Jan 16, 2003
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I know the power consumption (P=VI) goes down either when the frequency(current) goes down or the voltage goes down. The idea is to find a desktop cpu like a cheapo Sempron and underclock and undervolt the heck out of it. Will this have any negative physical damaging effect on the CPU?

A 1.8 GHZ Sempron is very cheap and only burns 62 Watts at 1.4V. Im guessing with a nice big fat heatsink I would be very safe at around 20Watts or less. How low would I have to go to achieve this?

Why would I want to do this? To build a little mini form PC that don't require a fan(No Noise) that I can put in the living room as a VCR.
 
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Lonyo

Lifer
Aug 10, 2002
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As long as it runs cool you don't need a fan. If you can get it at maybe 50 degrees c without a fan, that's not going to be a problem, but make sure it dsoesn't get too hot.
Good case airflow would help though.
 
Zap

Zap

Elite Member
Oct 13, 1999
22,377
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The cheapest Semprons don't have Cool and Quiet. If you were going for a more expensive one (IIRC 3000+ and up) then you can lower multiplier/voltage in BIOS (or use software like RightMark) and run it passively using one of those tower heatpipes designed for that purpose such as the Thermaktake Sonic Tower or one of those Scythe heatsinks.

If you were thinking ultra low budget, go for a mobile Celeron/P4. I have a mobile 2GHz Celeron running at about 1.22v in an Asus P4S800-MX board. I have an Arctic Cooling 4TC on it and with the case open the fan doesn't even spin continuously - I had to turn off the fan warning in BIOS otherwise the system wouldn't go past POST. :p Feel free to read up on the thread in this forum - search for Karaktu.
 
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Fresh Daemon

Senior member
Mar 16, 2005
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Have you considered a VIA Epia system, many of which are designed to be run fanless? It's no speed demon, but for a fileserver, firewall, even a low-to-mid-end HTPC (i.e. no HDTV encoding) it's plenty. Should be fine for your purposes. Will also pull very little power from the wall as well.
 
Gamingphreek

Gamingphreek

Lifer
Mar 31, 2003
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Originally posted by: Ready
I know the power consumption (P=VI) goes down either when the frequency(current) goes down or the voltage goes down. The idea is to find a desktop cpu like a cheapo Sempron and underclock and undervolt the heck out of it. Will this have any negative physical damaging effect on the CPU?

A 1.8 GHZ Sempron is very cheap and only burns 62 Watts at 1.4V. Im guessing with a nice big fat heatsink I would be very safe at around 20Watts or less. How low would I have to go to achieve this?

Why would I want to do this? To build a little mini form PC that don't require a fan(No Noise) that I can put in the living room as a VCR.
Click to expand...

Well there are 2 options:

A. VIA C3 System
B. AXP 2400+ 35Watt Mobile CPU <<<<
C. Pentium M

The C3 will be much slower than the others but it consumes no more than 8Watt of power. The AXP and the P-M will be comparable in power consumption and heat, with the nod toward the P-M, but the P-M will be much faster.

The XP-M is probably your best choice. THen just get a big copper HS unit and have fun.

Silent PC Review has some EXCELLENT articles on this topic. I believe the Scythe HS is wonderful for fanless cooling.

Finally, i believe you wish to build a HTPC (Home Theater PC). The C3 is probably not what you want. I have a 2400+ XP-M and even it lags when encoding and stuff, so you probably want to invest in the XP-M. THe P-M offers no advantage when encoding though, so you could get that.

-Kevin
 
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Fresh Daemon

Senior member
Mar 16, 2005
493
0
0
The XP-M is probably your best choice. THen just get a big copper HS unit and have fun.
Click to expand...

QFT.

You may find that some good, quiet fans (Yate Loon or derivatives like Nexus, Cooler Master, Glacialtech, Papst etc) undervolted to 7v or even 5v are completely inaudible anyway, and even a fan running at 5v is very much superior to no fan at all in terms of cooling. Running fanless is over-rated. I can't hear my Yate Loons at 7v unless I put my head right up to them.

 
E

entropy1982

Golden Member
Jul 10, 2005
1,053
0
0
Originally posted by: Ready
I know the power consumption (P=VI) goes down either when the frequency(current) goes down or the voltage goes down. The idea is to find a desktop cpu like a cheapo Sempron and underclock and undervolt the heck out of it. Will this have any negative physical damaging effect on the CPU?

A 1.8 GHZ Sempron is very cheap and only burns 62 Watts at 1.4V. Im guessing with a nice big fat heatsink I would be very safe at around 20Watts or less. How low would I have to go to achieve this?

Why would I want to do this? To build a little mini form PC that don't require a fan(No Noise) that I can put in the living room as a VCR.
Click to expand...

get a scythe ninja =P
 
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