Originally Posted by Defoler
Its nice that you read "hundreds of PSU reviews" but it still doesn't matter, as you did not read this PSU review.
Not all PSUs are the same, and you should know that pretty well.
Also your asumption that you can pull 25A from a 18A rail, is pretty funny.
It could have been correct if the PSU was working on this rail alone, and nothing else.
But clearly, this is not the case. There are other 4 rails, and all of them are being pushed.
So all this theory of yours, goes out the window.
I'm disappointed with you really. The fact is that you did not bother to look up on this particular PSU, and you are talking a lot on something you don't understand.
Also I will say it again.
You can't pull 138% of the amp from a rail without causing damage to it. The cables, resistors and the connection board is not designed for this increase.
The sata cables and molex cables are designed for 75w. You are going to recommend him pushing 100w+ on these cables?
900watt is irrelevent. You are telling him to push a 216w rail (and 75w calbes) to its limits. Awesome...
Defoler ... first off, I'm not TELLING him to do anything. I'm saying it's not dangerous to TRY.
And 900W is NOT irrelevant. It is by far the most pertinent statistic here. The only reason the rail values have any importance is that they may suggest the more favorable ways to arrange the wiring.
In my 2nd post, after pondering the situation overnight, I told the OP that he should make up one of the 6-pin connectors using the molex cables, and for the other 6-pin he needs, to split one of his eight-pin cables into two six-pins.
Of course, (and I probably should've spelled this out) this means he should be using TWO dedicated molex cables to make up the first 6-pin connector. Now, if each
cable is rated for 75W (according to you), why is it that you think it's unsafe to combine TWO 75W cables into ONE cable ... that's *supposed* to (with GPU at stock) only pull 75W through it?
That's only about, what, around 6.25 amps we're talking about here? Which leaves him 10.75A to run whatever else he needs to off that rail + whatever extra headroom there is due to the OCP being set higher than 18A, which, like I say, it is certain to be.
I dunno why you're so obsessed with the 25A number I threw out, it's not a calculation of what's going to be needed
I'm just saying you could
probably get away with pulling 25A though it if you needed to, because the OCP circuit on your average 18A-rated 'rail' is actually set at around
25A. And it's NOT GOING TO HURT ANYTHING IF YOU DO. The worst-case scenario is that the PSU will shut off.
If you think they use wires on an 18A 'rail' that cannot safely have 25A pulled through them, you are wildly mistaken. And I dunno WHAT you're talking about with 'connector boards and resistors' not being 'designed for the increase' ... all that matters is what the OCP circuit is set to, amperage-wise, and whether the wires that make up the 'rail' are of sufficient gauge, which they are.
And as far as splitting the eight pin into two six-pins, that is a cable rated at 150W. I'm telling him to split it into two 6-pin cables. Which are supposed to only have 75W each pulled out of them, if the card is at stock. Right? So how is this so dangerous?
In fact, splitting both the 8 pins into two six-pins is probably the 'best' option here, but those splitters cost money, whereas he probably has two molex->6-pin connectors already laying around, and frankly those should work fine, too. For the reasons I described above. So buying one 8-pin to 2x6-pin splitter, and using two molex adapters, should work perfectly, and is the cheapest possible option (EDIT: Please see 'Belated Edit' for more on this above)
Bottom-line, I stand by what I said above. I know *exactly* what I'm talking about, and your implication that I'm suggesting something wildly stupid and dangerous (roughly what you're implying here) is totally off-base Defoler.
Originally Posted by GameBoy
And yes, the PSU does have 72A on its +12v, the traces are just split up and monitored separately/individually by the OCP circuit. It works 99% identically to a single rail.
Exactly. It rather seems to me, based on DF's statements throughout this thread, that he believes that 'rails' consist of independent power supplies within your power supply, and thus individual rails can become dangerously overloaded.
This is what is leading him to draw incorrect conclusions about the nature of this particular endeavor (and mistakenly call us all a bunch of 'dummies').
It appears that he is unaware that the 12V 'rails' are nothing but collections of wires, all hooked up to the SAME 72A power source (on this PSU), with OCP circuits on them that are set to trip at a particular amperage.
The 'rails' are a not independent little power supplies, rather, they are just a 'protection' feature that allow the PSU makers to get away with running higher gauge (i.e. cheaper) wires. With OPC circuits on various collections of wires, there becomes no chance that the entire amperage of the unit could be drawn through one single plug, like it theoretically could be on a single 12V rail unit. Ergo, cheaper wires can be used coming out of the psu.
The vast majority of the time, however, these OCP circuits are set to trip at a considerably higher amperage than the spec set out on the box, and the actual wiring itself is of a significantly
lower gauge (i.e. thicker) than what is actually required to handle the amperage specified as a max by the OCP that the wires are attached to. It's done this way to allow for flexibility in the way things are hooked up, whilst still providing some measure of protection.
Ergo, there's nothing 'dangerous' at all about 'overdrawing' the amperage on any 'rail' of a multi-rail power supply. Either the OCP circuit that defines
that 'rail' will allow your components to draw (off of the 72A source) what they are trying to draw, or it won't ... in which case, the PSU shuts down.Edited by brettjv - 5/12/11 at 3:53pm