Watts vs Amps: Which is more important

[WeatherDave]

I've been tasked with rebuilding some older desktops. These were custom machines, in all about 500, built from parts back in 2006 by one of our vendors. Facing replacement, we looked into reusing them across the organization for basic office machines instead of just sending them to be recycled.

As I investigated the machines, the Power Supply seems to be an issue. They came with OEM 350W Coolmax's (300W combined 12v1 and 12v2), which seemed to work very well in the field (few replacements).

Since these will be basic office machines (you know the type, office/intranet apps/etc...) they don't need much. However as I looked at CPU's (say a Core i3-21xx) on Intel MB's (say BOXDH67GDB3) I notice Intel's recommendations are for 35amp combined (20 on 12v1, 15 on 12v2).

To me, this seems high. given that the machines will be using integrated graphics, 4G of DDR3, a HD and a DVD, total wattage is only like 200-250. Throw in a 2100T (35W CPU), and it's on the low end of that 200W range.

So my question: is Intel overstating the necessary 12v amperage, and do you think I really need to upgrade to like a 450-500W PS, given the limited necessary functionality of the machine?

Appreciate your thoughts,

Dave

 

[dma0991]

The Core i3 2100T is pretty efficient when it comes to power so I wouldn't worry about anything. The OEM PSU is way more than enough than what the whole rig would require. If it is true that Intel recommends 35A that would mean that the whole rig needs 420W to power the whole thing which is absurd.

I am 100% sure that Intel is just overstating the requirements and if you're not sure you could rebuild a single PC with that PSU and run a stress test on full load(burn-in) to be certain that the PC will hold. If that is able to run 24 hours without issues you could rebuild the rest.

 

[VirtualLarry]

My older rig with a Gigabyte G31 board and an E5200, even overclocked to 3.0 from 2.5, and one 7200RPM HD and one DVD drive, and one stick of RAM, idled at 40W, and under full Prime95 load, took only 80-85W.

I think that you would be fine with a 300W PSU.

 

[Ayah]

Actually, you could run those on a 120W PicoPSU.

 

[WeatherDave]

Thank you everyone as these responses validate my suspicions.

Firstly I found it suspicious that the 12v A values on the Intel spec sheet were both 20A. Isn't that the maximum values allowed under ATX12V specs?

Secondly, every every benchmark I've seen (from a plethora of sites) show the power usage of the i3-21x series were way under 150W. So why require that much power? I guess maybe because that MB supports an i7, as well as a PCI-E slots. So in that regard I guess I can see the reason for the inflated value.

I was simply concerned that the processors were requiring some specific 12v minimums in order to operate.

Thanks again.

Dave

 

[BoomerD]

Hell, I'd be scared to have a Coolmax PSU in my computer, especially for a work situation where the loss of data could be costly...

From what I can tell, the 300 watt Coolmax PSUs are made by ATNG, NOT one of the better manufacturers out there...but also, not one of the worst.

 

[Modelworks]

Power requirements for any device has two ratings, one is continuous and the other peak. Things like hard drives draw more current when first switched on. The same goes for the motherboard voltage regulation for the cpu. A circuit might show a continuous usage of 10A but may need 12A to get started and run continuously. If you go too low on requirements then devices may work but eventually they will cause the supply to fail.

The general rule I use is 10% minimum over what something needs to run continuous. If it involves motors then I go 20% over. There are some other things to consider like wire size and how long it takes the full current to be available but keeping a 10% margin over what the device needs generally works well. Higher margins are fine if cost allows.

 

[StrangerGuy]

Hell, I'd be scared to have a Coolmax PSU in my computer, especially for a work situation where the loss of data could be costly...

From what I can tell, the 300 watt Coolmax PSUs are made by ATNG, NOT one of the better manufacturers out there...but also, not one of the worst.

Yeah, OP needs to dump those crappy PSUs right now. It doesn't pay to gamble your PC and data when a quality unit can be had for ~$40.

Just because some cheap brand claims to do 500W doesn't mean it can actually deliver clean and stable power anywhere close to the rated wattage. Most of them won't even do 200W before they blow themselves up. If lucky enough, only the PSU is dead...If not the whole system goes kaput.

 

[yottabit]

Yeah, OP needs to dump those crappy PSUs right now. It doesn't pay to gamble your PC and data when a quality unit can be had for ~$40.

Just because some cheap brand claims to do 500W doesn't mean it can actually deliver clean and stable power anywhere close to the rated wattage. Most of them won't even do 200W before they blow themselves up. If lucky enough, only the PSU is dead...If not the whole system goes kaput.

For 500 machines? How bout he doesn't spend the $40 on each PSU, and buys a brand new Honda Civic instead

The OEM PSUs will be fun so long as they are still functioning correctly.

Personally I would also look into the Athlon II line. You could definitely get some savings doing something like an Athlon II x2 250 across the board and that should still be more than adequate for office work.