Max power draw for a mid-high end system = 240W.

Inazuma

Inazuma

Inazuma

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I was recently looking into buying a new graphics card but was worried my PSU wouldn't handle it. It's a Corsair 620W and I've had it for years (maybe 5?). In that time it's been through several builds. The latest being an Intel Core i7 and Geforce 460 GTX with a PCI audio card, four ram sticks and three hard drives.

So I bought a Belkin-branded wattage monitor. Turns out I'm only drawing about 75W when doing basic tasks (internet browsing) and max 240W when doing benchmarks.

As I said earlier, I was thinking about buying a new graphics card. A 680 GTX only draws 45W more than the 460, bringing the total to 285W. Even if I had two of those bad boys, my draw would only come to 480W.

So could someone please explain to me, as an enthusiast consumer, in what situation I would ever need anything more than my current PSU, or in fact something even lower. I mean it sounds like for most people a <450W PSU will do just fine.
 
Because:

A) PSU degrade over time. 620W might actually be 550W now (probably not this greater drop but you get the picture).

B) Power isn't supplied exactly where you need it, so you might become limited on 12V rail current balance.

C) Peak draw is almost certainly higher.

D) A GTX680 is 200W max TDP. A Core i7 at full load is 95 or 130W depending on what chip + overheads means theoretically your machine fully loaded is the best part of 350-375W.

I know my Mac Pro (980X + 6870) hits the best part of 400W when fully loaded so your 240W figure is... wrong!
 
true i have a 450W running all of mine, but people like headroom as you tend to get problems running anything at full whack and small voltage drops can result in games crashing.

You also have to consider that the full wattage wont be available on the 5v rail so you may only be using 50% of the total wattage but you may be pushing 80-90% on the 5V rail.
 
My current system is drawing under 40w in idle and 130 max load.

i5 3470 with 7770 graphics card.

I had a gtx 670 with 2500k and the max power consumption I saw was 240w. Don't forget that wall readings are higher than what is actually loaded on the power supply because of efficiency. 270 seems about right for a 680 with a modern efficient cpu, but fully stressing both at the same time might push it a bit higher.
 
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What's even worse is that your PSU will run at a given efficiency. Say 85, 90% to be generous. So that's an extra 10% that isn't actually drawn from your components. If you pull 240W at the plug, your components actually use 220W.

The problem with the HX620, despite being old, is the lack of 8 pin connectors (at least mine). 6 pin connectors are rated for 75W draw, 8 pin connectors for 150W draw, and you have 75W coming from the PCIE slot.

So in theory, a card with a 6 pin + 8 pin connector should only be allowed to draw 300W max. But they rarely use that much power in the first place. Typically, under 200W. A 6->8 pin converter will be fine if your card's max power draw is under (75W x 3), 230W, which would be above what a GTX680 would need at full tilt.

Bottom line, given that good PSUs are over-specced, you should be fine using a GTX680 on a 6 pin, and with the addition of a 6->8 pin converter.

.... if my calculations are correct. :D
 
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Components in the PSU especially capacitors and similiar have a finite lifetime thats dramatically shortened at higher temperatures (i.e. at 65C it might last 10-15 years, 80C 5 years, 90C 2 years - just as an illustration) and heavier loads and thats before you consider how "clean" the supply of power is.

So over speccing on the PSU means your supplying a "cleaner" signal that reduces degredation of components and increases stability while reducing the chance of the PSU going wrong any time soon.

A lot of the reason for why the general advice is fairly over spec is due to say someone having a system that required 300watt peak - you'd reccomend them say a good quality 400watt but they'd go away ignore your advice and buy a cheapy no name 400watt which struggled to actually manage half that stable, by reccomending 500-600watt hopefully they'd atleast buy a cheapy 500-600watt that could do half that reasonably well. More than once I've reccomended someone buy say a 400-450watt corsair, OCZ, etc. and they've come back to me bitching about how I said 400watt (or whatever) would be enough only to find they went away and bought a 400watt q-tec then saying I gave them bad advice.
 
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