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PCI-E Adaptors

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a b ) Power supply
November 30, 2010 6:49:36 PM

I want to run 2 graphics cards off my PSU but each card needs 2xPCI-E and the PSU only has 2 in total.

I have some of these 4 pin molex to PCI-E adaptor cables so the question is.

Do the 4 pin molex cables supply the same current as the PCI-E cables?

and

Is there any reason why its not a good idea to use them?

Thanks. [:bohleyk:1]

More about : pci adaptors

a b ) Power supply
November 30, 2010 6:57:05 PM

If your psu is not up to the job you can get instability issues during high gpu load situations, you will only know when you use them (band aid solution).
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a b ) Power supply
November 30, 2010 6:59:30 PM

The PSU is up to it, 700w OCZ, I just wanted to know if these connectors work exactly the same as a PCI-E cable.
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a b ) Power supply
November 30, 2010 7:11:45 PM

On the branded supplies (ocz, coolmaster, antec, all the good ones) usually each of the 6pin pci-e connectors and the 4pin cpu connectors have a seperate 12v rail to stop voltage fluctuations between devices in the system.
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a b ) Power supply
November 30, 2010 7:15:22 PM

So your thinking the 4 pin molex connectors won't have this?
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a b ) Power supply
November 30, 2010 7:29:00 PM

normally the standard 4pin molex and sata power connectors share the voltage rails with each other in parallel.

24 pin atx connectors can have a 2 seperate 12v+ rails.
4 pin cpu connector usually have a seperate 12v+ rail each.
6 pin gpu connector usually have a seperate 12v+ rail each.
all 4 pin molex and sata power connector normally share the 12v+ rail.

again it all depends on the supply manufacturer.

cheap £15-30 supplies share all the rails with each other, so say one of your gpu's need more power it reduces power to all other components, this can cause system instability.
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:00:34 PM

hairystuff said:
On the branded supplies (ocz, coolmaster, antec, all the good ones) usually each of the 6pin pci-e connectors and the 4pin cpu connectors have a seperate 12v rail to stop voltage fluctuations between devices in the system.


that's not true. more often then not they all use a single 12v rail that has been split 2,3, 4x
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:04:32 PM

beanoslim said:
I want to run 2 graphics cards off my PSU but each card needs 2xPCI-E and the PSU only has 2 in total.

I have some of these 4 pin molex to PCI-E adaptor cables so the question is.

Do the 4 pin molex cables supply the same current as the PCI-E cables?

and

Is there any reason why its not a good idea to use them?

Thanks. [:bohleyk:1]



are you running the GTX 460 or ATI 6850? you will be ok, they don't draw that much power plus you already own the PSU. just run one 6-pin to each card and then one adapter.
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a b ) Power supply
November 30, 2010 8:16:09 PM

@dipankar2007ind, I've used this one in the past and its been faithful.

OCZ 750W Fatal1ty Series Modular PSU - 4x PCI-E 6x SATA
http://www.ebuyer.com/product/235519
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a b ) Power supply
November 30, 2010 8:20:13 PM

ct1615 said:
are you running the GTX 460 or ATI 6850? you will be ok, they don't draw that much power plus you already own the PSU. just run one 6-pin to each card and then one adapter.


The PSU is the OCZ Modxstream 700w.

The cards are 2x GTX460's.

What is the reasoning behind having one in each?

Thanks.
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a b ) Power supply
November 30, 2010 8:25:40 PM

@ct1615, I had built a couple of gaming rigs in the past using the multi railed coolmaster psu and the system worked perfectly without any downtime or stability issues, before that I used a Antec truepower 700w psu (came with a titan series case) and the thing blew after 8 hours of gaming, the gpus used in one machine was a 2x 9800GTX and the other was a 2x 480GTX, both systems had 6x sata hdds setup in raid spaning and 2x dvd burner.
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a b ) Power supply
November 30, 2010 8:29:45 PM

So do you think my psu has the seperate 12v rail in the molex?

I wont have a lot of other demanding gear attached so I'm banking on the 700w being enough.

Just don't want to push the wrong type of feed into the cards..
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:29:48 PM

beanoslim said:
The PSU is the OCZ Modxstream 700w.

The cards are 2x GTX460's.

What is the reasoning behind having one in each?

Thanks.


the two 6-pin are probably each on their own split 12v, the adapters are probably on the same split that provides power to the HDD, fans, optical drive.
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:36:06 PM

hairystuff said:
@ct1615, I had built a couple of gaming rigs in the past using the multi railed coolmaster psu and the system worked perfectly without any downtime or stability issues, before that I used a Antec truepower 700w psu (came with a titan series case) and the thing blew after 8 hours of gaming, the gpus used in one machine was a 2x 9800GTX and the other was a 2x 480GTX, both systems had 6x sata hdds setup in raid spaning and 2x dvd burner.


...ok...what does that have to do with the OCZ unit beans owns? plenty of truepowers run SLI set ups and yes antec does have dud units out there, CM has more but as you prove they also have capable units.

as for 12v rails

What is "multiple +12V rails", really?

In most cases, multiple +12V rails are actually just a single +12V source just split up into multiple +12V outputs each with a limited output capability.

There are a few units that actually have two +12V sources, but these are typically very high output power supplies. And in most cases these multiple +12V outputs are split up again to form a total of four, five or six +12V rails for even better safety. To be clear: These REAL multiple +12V rail units are very rare and are all 1000W+ units (Enermax Galaxy, Topower/Tagan "Dual Engine", Thermaltake Tough Power 1000W & 1200W, for example.)

In some cases, the two +12V rail outputs are actually combined to create one large +12V output (Ultra X3 1000W, PC Power & Cooling Turbo Cool 1000W, for example.)


http://www.jonnyguru.com/forums/showthread.php?t=3990
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:41:18 PM

Quote:
Can you explain me your sig?CT


what's to explain? i was the runner up in a contest for being such a nice guy! :D 
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a b ) Power supply
November 30, 2010 8:44:14 PM

I've never been keen on using the splitter/adapters that come off the molex connectors, as time progresses they've caused reliability issues in the past (common issue hard drives spin down unexpectedly which has nothing todo with power management). Only just saying as a precaution.
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:48:13 PM

i'm not saying its ideal or you shouldn't purchase a PSU with 4x power connectors if you plan to run two cards that need two power connection each.

beans already owns the PSU, its solid and has enough 12v power, he should see how it handles the set up. i've run cards off the adapter with no 6-pin power connections, they ran just fine so I know it can be done.
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a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 8:48:54 PM

Quote:
What is that award for?


its a joke ;) 
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a b ) Power supply
November 30, 2010 9:03:14 PM

I suppose it would be ok, he is using a good brand psu with plenty of protection. I thought the CT1615 was a reference to Creative Labs or Cirrus Logic.
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a b ) Power supply
November 30, 2010 9:09:41 PM

What type of critter is that^ :lol: 

Ok, thanks for all the input, from what ct says I think I'll give it a go and see what happens.

If the worst case senario is instability or power downs like hairy says then I can live with that, just wanted to be sure that there were no known reports of serious malfunctions..

I do plan a psu upgrade when I update my system but for now it'll save me having to buy one. [:fisshy:7]
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Best solution

a c 164 ) Power supply
a c 235 U Graphics card
November 30, 2010 9:18:56 PM

beanoslim said:
What type of critter is that^ :lol: 

[:fisshy:7]



http://en.wikipedia.org/wiki/Ferret
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a b ) Power supply
November 30, 2010 9:24:11 PM

HOLY S*IT, THAT THINGS REAL!!
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December 1, 2010 3:05:01 AM

Лол

This thread is going nowhere. LOL.

Great pic of that critter.
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a b ) Power supply
December 2, 2010 2:00:20 PM

Best answer selected by beanoslim.
n
nAnd the award for best answer goes to critter chops :lol: 
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a b ) Power supply
a c 271 U Graphics card
December 2, 2010 7:58:10 PM

This topic has been closed by Mousemonkey
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