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PSU for tri-fire?

RichH

RichH

RichH

Associate
Joined
1 Dec 2011
Posts
434
I currently have a 2500k and 2x 7950 on a OCZ 850w gold rated PSU. All components are heavily overclocked.

Reckon I could squeeze in a third card, or is that new PSU territory?

Thanks in advance.
 
RichH said:
I currently have a 2500k and 2x 7950 on a OCZ 850w gold rated PSU. All components are heavily overclocked.

Reckon I could squeeze in a third card, or is that new PSU territory?

Thanks in advance.
Click to expand...

I would look at a bigger PSU you may go over if you oc a lot.

I have 2 x 7970 matrix platinums and a hexcore and when oced they pull 910 watts at the wall.
 
I had to upgrade from my HX1000 to a 1500w when i got my three 7970s

Not sure what the draw comparison is between the 50s and 70s ?
 
Wow ok, 2 questions.

How do you test power draw? With one of those plug in at the socket multimeters?

What happens if you try to draw more power than the PSU can supply? Throttling, crash, explosion?
 
According to this a stock 7950 draws upto 300w and a 7970 upto 350. Scary stuff! I'm surprised my OC hasn't already burst into flames!
 
RichH said:
What happens if you try to draw more power than the PSU can supply? Throttling, crash, explosion?
Click to expand...

Quick lesson in power for you.

80+ means that a PSU can remain efficient at the rating. So for example (forgive me if I'm a % or 2 out it's been a while !) if you have a 800w 80+ bronze PSU your PSU will remain efficient (IE not create waste power which turns into heat) at 82% of the full load. So basically you can put out about 700w before you start to go over 82% and thus the PSU then starts to become inefficient and get hot. The heat is basically wasted power.

The higher the 80+ the more efficient the PSU is at the given %. IIRC gold is about 90%? or am I thinking platinum?

Basically the way they make these psus is to make them as higher powered units, then downgrade the overall wattage to make sure they remain efficient.

I used to run a 625w Modu II by Enermax. I had it pulling over 800w at the wall with Quad SLI 295s and an overclocked Core 2 Extreme.

What is dangerous is when your PSU starts to put out distorted power (aka ripple) this causes spikes and dips and is what leads to dead hardware.

I've seen a 500w NZXT Hale put out over 800w and still refuse to die, but they were as or more expensive than a 800w PSU and why they were 80+ gold.

Ideally you don't want to push higher than the rated 80+ rating because then you create waste heat and that costs you money, so ideally you want to calculate your maximum power draw then get a PSU that you will only draw 2/3 of the stated power.

HTH
 
NP.

If you're an avid hardware fan then a good top end PSU is always a good investment.

The price will sting (think Corsair AX or Enermax Platimax/Revolution) but it's worth it in the long run.

Thankfully my Alienware case came with a 1200w 80+ Silver unit so I don't think I'll ever need another one.
 
ALXAndy said:
Quick lesson in power for you.

80+ means that a PSU can remain efficient at the rating. So for example (forgive me if I'm a % or 2 out it's been a while !) if you have a 800w 80+ bronze PSU your PSU will remain efficient (IE not create waste power which turns into heat) at 82% of the full load. So basically you can put out about 700w before you start to go over 82% and thus the PSU then starts to become inefficient and get hot. The heat is basically wasted power.

The higher the 80+ the more efficient the PSU is at the given %. IIRC gold is about 90%? or am I thinking platinum?

Basically the way they make these psus is to make them as higher powered units, then downgrade the overall wattage to make sure they remain efficient.

I used to run a 625w Modu II by Enermax. I had it pulling over 800w at the wall with Quad SLI 295s and an overclocked Core 2 Extreme.

What is dangerous is when your PSU starts to put out distorted power (aka ripple) this causes spikes and dips and is what leads to dead hardware.

I've seen a 500w NZXT Hale put out over 800w and still refuse to die, but they were as or more expensive than a 800w PSU and why they were 80+ gold.

Ideally you don't want to push higher than the rated 80+ rating because then you create waste heat and that costs you money, so ideally you want to calculate your maximum power draw then get a PSU that you will only draw 2/3 of the stated power.

HTH
Click to expand...

Few errors in this, it's a lot simpler than you're making out.

For us (UK), the 80 Plus system is based on 20-100% rated load on 230V.

http://en.wikipedia.org/wiki/80_Plus#Efficiency_level_certifications

I'm not sure where you are getting the 82% cut off point?

If the PSUs are certified they should be at least as efficient at 100% load as they are at 20%. (Plus Titanium is the only exception to this)

Now I wouldn't run a PSU for long periods over 90% load, but that's not due to it's efficiency level, but it may help the lifespan of the PSU. That's just my preference.

Also it should be noted 80 Plus is tested at ambent temperature, so if you have a poor case that gets hot you probably won't get the certified level of efficiency even at low usage levels. This is why most new gaming/high end cases have bottom fitting or seperated PSU mounting positions to keep the heat from other components away from the PSU.
 
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