PSU and Temperature - Tech Question

Aunty Em

Aunty Em

Well-Known Member
I have just put a 400w PSU into my system which was running on a 300W PSU. On checking the temperature of the CPU I find it has dropped dramatically from an average 46C to 38C not under load. Why is this?
 
I seriously doubt that changing the power supply could affect the temperture of the CPU. After all, regardless of the power supply, the CPU is still going to draw the same amount of current and produce the same amount of heat (that is wattage). Could be that the newer power supply provides better ventilation than the prior power supply, i.e, stronger fan...hard to tell though.
 
I jumped my FSB from 135 to 139 & had a 10F drop. Methinks it's winter.
 
That's what I'm thinking too. My psu has a fan attached on the front an back on one of my comps. Maybe, the new one just produces less heat inside the case?
 
PostCode said:
Could be that the newer power supply provides better ventilation than the prior power supply, i.e, stronger fan...hard to tell though.
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You could be right about the ventilation on the unit because the exhaust from the fan feels stronger and warmer than before - either that or it's my imagination. The system temperature is also down by about the same amount and it's been running for a while now, so it's up to what could be considered it's normal working temperatue.

It's a switching supply as well, aren't they supposed to create less heat anyway?
 
Gonz said:
I jumped my FSB from 135 to 139 & had a 10F drop. Methinks it's winter.
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This room is usually at a fairly constant temperature summer or winter, that's why the computer is in here.
 
Does it have a second fan lowing down towards the CPU that the old PSU didn't have? That may be the answer. I had the same result when I slapped in a PSU with the internal fan.
 
HomeLAN said:
Does it have a second fan lowing down towards the CPU that the old PSU didn't have? That may be the answer. I had the same result when I slapped in a PSU with the internal fan.
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I think you just hit the nail on the head.:) It does have a second fan, although it also has noise suppression so I can only just hear it. In fact it's quieter than the smaller PSU.
 
another thing is it may not be getting quite as hot as the other one, thus less heat in the case, is the case temp down a bit?
 
Justintime said:
another thing is it may not be getting quite as hot as the other one, thus less heat in the case, is the case temp down a bit?
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Yes - I've just had it running at load with the CPU @ 45C (49C before) and the system temp @ 35C (38C before), so it does seem to be reduced about 3-4C.
 
I just went from a 300W PS to a 400W the other day, and my CPU temp has been hovering around 44C or so. I think it was at 46. The new power supply has a fan on the back to exhaust heat, and another one on the opposite side, rpesumably to draw air into the PSU.

My 300W PS was working fine, but I needed to replace a 235W PS for a computer (K6-2/300) I was putting together for my brother in law. Anytime I hear a loud pop and see a bunch of dust suddenly fly out of the power supply's fan, I'd say it needs to be replaced. So I drove over to CompUSA and found I could pay $27 (or was it $28?) for a 250W power supply... or pay $30 for a 400W they had on sale (CompUSA brand, but still). So I bought the 400W, stuck it in my system, and put the 300W in the 300 (@333) system. So now we both have more power supply than we really need, but it's all good.
 
Inkara1 said:
So I drove over to CompUSA and found I could pay $27 (or was it $28?) for a 250W power supply... or pay $30 for a 400W they had on sale (CompUSA brand, but still). So I bought the 400W, stuck it in my system, and put the 300W in the 300 (@333) system. So now we both have more power supply than we really need, but it's all good.
Click to expand...

Mine cost about $30.11 plus postage of $7.13, so I'm happy. It's a Mercury. I bought it from a dealer in Perth, Scotland through eBay. So I grilled him by email first to make sure it was what I wanted. I also needed a power switch on the back so that I can turn off the power to the computer when I shutdown as my cable modem runs from the same power source and surge protector and has to stay live all the time. After checking his ratings, which were several hundred positives against 2 or 3 negatives I reckoned that was OK and he gives the usual 1 year warrenty on OEM goods. :)

I checked the local shop first but they said they'd have nothing till after christmas and then it would be almost double the price for the same unit! As I'm upgrading the board and memory after christmas and the cpu and heatsink about 4 weeks later I wanted to make sure the PSU was big enough to cope and that there were no problems with it first. It also means that if I do get a new case later in the year(which is very likely) I have all the spare componants I need to rebuild a second computer with this board and processor which I intend to overclock and network. I've decided to let my daughter carry on using her Intel Celeron 500 as it does everything she needs for the moment.

I'm led to believe that having a bigger PSU means that it doesn't have to work as hard to supply the required power. The guy in the shop told me that.:)
 
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