Originally Posted by Defoler
I didn't "forget" anything.
I actually bothered to open another web page, google a few reviews which included an over-current run, and use my eyes to read them, and understand the PSU before I recommended something.
Also, I don't get you. Really I don't.
You are actually saying "hey, try it out, and if your PSU blows up after a few days because it couldn't hold to the OCP high usage over time, replace your PSU"?
Is that very smart to suggest?
Also are you serious? 25A?
Even the AX1200 doesn't have that big of a margine before OCP kicks in.
The X7 is a good PSU, but its not amazing one that can give you 38% extra on a rail. Don't be rediculous.
I actually prefer to say "don't risk it" instead of "try, if it blows, replace".
First off, to be clear, I didn't mean for it to sound like I'm criticizing your stance in telling the OP 'better safe than sorry'. I'm merely sharing my own perspective on the subject, and it appears that I believe that the 'risk involved' with trying
the OP's prospective arrangement ... is significantly lower than you do. Everyone's entitled to their opinions
But, with all due respect, DF, I've 'bothered' to read hundreds of PSU reviews in the past
And that's how I know that it is highly unlikely that a '18A rail' on a 900W PSU is going to actually be locked down at 18A. There is definitely going to be leeway there, they are never locked down at the exact amperage specified on the box. Maybe it won't allow 25A, but it's going to be more than 18A, for sure. 25A is far from a 'rediculous' estimation. It may turn out to be slightly off, but it's perfectly 'realistic' to guess at this amount, absent the actual facts of the situation.
What the AX1200 does is fairly irrelevant to this equation. In fact, it's probably more likely that a very high-end unit like that would have more 'strict' OCP circuits defining it's rails.
Now, if you know for a fact from a review what the actual amperage is that can be pulled through that particular 'rail' on the OP's particular psu, please do share the review with us so we can see where we're at
Also, even if there was 'voltage drift', which, as I say, only applies if the entire PSU is being pushed to capacity (the concept does not apply to individual 'rails', save on an HX1000), that 18A rating is still based on amperage
. I.E. even if your overall 12V circuit dipped to 11.5V due to the PSU being at capacity, you're still going to be able to pull the same total amount of amperage through that 'rail' before tripping it's OCP.
Another thing I'd point out is that if you believe, as you appear to state above, that 150W is the maximum that can be pulled out of two 6-pin PCI-Ex connectors, you are mistaken on this point. That is just the spec that the card makers are expected to adhere to. Once you start OC'ing, you certainly could
pull more than 150W out of those connectors, because the card is no longer in 'spec'.
The actual maximum that can be pulled from every connector on your PSU is dictated by the amperage allowed by the OCP circuit on the 'rail' it's connected to (not applicable to single-rail PSU's), or the OCP on the entire unit, or, worst-case scenario, the gauge of the wiring itself.
Obviously, the OP doesn't want to spend money he doesn't have to, otherwise he wouldn't be on here asking if he can make do w/what he has. 900W is, in theory, enough power for this rig.
Ergo, it SHOULD be possible, through one wiring scheme or another, for it to be able to support the third card. Yes, it will be running close to spec if put under full load, and in fact it's possible that his OC'ing capability on the cards will be limited. But he should almost certainly
be able to make it work with the cards at stock.
Lastly, it is extremely unlikely that PSU would 'blow up' due to what he's trying here. We're not talking about an Allied/Deer or Raidmax piece of crud PSU, and therefore, if you draw too much current, either through a particular 'rail', or on the unit as a whole, the PSU will shut down, not 'blow up'.
All PSU's have an OCP circuits at the level of the entire PSU, the reason it's there is EXACTLY to protect the PSU from 'blowing up' when too much current is drawn. And OCP circuits are like 100 year old technology, so I think they pretty much 'have it down' at this point
Only the cheapest junk PSU makers flub this piece of the equation and fail to use adequate components to protect the unit and your system.
OP ... most likely the best thing to do here is going to be to fashion one 6-pin connector through the molex cables, and the other through splitting one of the PCI-Ex 8-pins (EDIT: Please see 'Belated Edit' in the above thread
Hook up your other 3 PCI-Ex connectors, one per GPU. Then make use of your 3 'adapted' cables as the 2nd connectors on each of the three.
Like I say, it's possible your OC'ing capability may be limited somewhat using this PSU. It's also possible that you'll have to try various wiring schemes to get it working right. And it's also possible that over time the unit will degrade faster than it would if you weren't pushing it hard. But I'm talking it's like the difference between the PSU lasting 5 years instead of 10 years.
And let me just state for the record that I would NOT suggest something to someone if I thought they were putting their system at risk, esp. not w/o making significant disclaimers to that effect
If you don't have the money right now for a new PSU and want to get this going, and don't mind your OC'ing perhaps being limited for a time until you get a new PSU, you should
be able to get this setup safely working on your current PSU. It may take some patience and trial/error but it is highly unlikely (note: not impossible)
that you are risking damaging your system, 'blowing up' the PSU, etc.Edited by brettjv - 5/12/11 at 3:47pm