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Need instructions for spliting power from a 6 pin PCIE to 4 pin molex.

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November 29, 2007 8:54:02 PM

Hi I have a Dell dimension E510 and the stock psu with 305 watts(dual 12v rails, 22 amps). Dell underrates their psu's. I've asked around and people say that I can run a 3780. But it seems that I don't have a 6 pin PCI express connector so I was wondering how to split the power from a 4 pin molex power connector.
What are the necessary steps in doing this?

Thanks.

a b U Graphics card
November 29, 2007 9:01:48 PM

It would be as simple as plugging the splitter in to a free connector from the psu and then to the card, now for the bad news, you can't put a dual slot card in your box.
November 29, 2007 9:12:28 PM

I already know that I cannot put dual slot cards. Im going to wait for the single slot solutions. ex. heat pipe. What is the splitter? is it something I buy?
Or is it the converter from 4 pin to 6 pin?
Related resources
November 29, 2007 10:08:59 PM

The splitter will work.

FYI: At one point in time there was an issue with the splitters that you could buy on newegg. You had to cut one of the wires for it to work...
November 30, 2007 2:45:04 AM

In that picture, the black pin is the 4 pin and the white ones are the 6 pin PCI express, or do I have it flip flopped?
a b U Graphics card
November 30, 2007 3:55:34 AM

You have it flip flopped.
That splitter and the extension that Dale showed you are what others have used together.
November 30, 2007 8:37:35 PM

So I would just have to buy the cord, plug the black pin into the graphics card and then plug one of the white pins into a 4 pin from the mobo.

right?
a b U Graphics card
November 30, 2007 9:15:18 PM

Yes, providing there is enough room on the cable for it to reach.
On the other forum you were shown a Molex splitter, most people have had to add that as well, in order to reach the card.
November 30, 2007 9:28:16 PM

What do you mean?
Do I have to buy the splitter that Dale showed me and an extension? Can you give me links to both at Newegg?
November 30, 2007 9:58:21 PM

Check the length of the wires on your PSU, you might not need an extension.
November 30, 2007 10:26:24 PM

aznstriker92 said:
So I would just have to buy the cord, plug the black pin into the graphics card and then plug one of the white pins into a 4 pin from the mobo.

right?


No. You plug BOTH white molex connectors to the power supply molex, NOT the mobo.
December 1, 2007 3:25:49 AM

MrMr said:
No. You plug BOTH white molex connectors to the power supply molex, NOT the mobo.
I missed that completely. He would be hard pressed to find a place to plug it in.

I think that two Molex connectors are provided so that you can put them on different rails. Since I am sure that PSU only has a total of two rails and one of them is dedicated to the mobo, then you can use only one of the Molex connectors. Using both would be redundant.
a b U Graphics card
December 1, 2007 8:50:37 AM

MrMr said:
No. You plug BOTH white molex connectors to the power supply molex, NOT the mobo.


I missed that too, but I figure he would have known that there aren't any four pin power leads coming off his motherboard, and Zorg has explained the rest.
December 1, 2007 7:00:04 PM

Ok when I put mobo, I meant the psu.
So now im confused. One person is telling me to try to plug 2 4 pin molexes, and another is telling me to plug one in.

Heres what I think.
1. I buy the molex
2. plug it the 6 pin side in to the card
3. plug one(?) molex into the extension (if needed)
4. plug the extension into the psu(but where on the psu? the 4 pin from the psu?)

If not using the extension, I
Do 1. and 2.
3. plug one(?) molex into the psu. (4 pin?)

I think I almost have this.
a b U Graphics card
December 1, 2007 7:25:48 PM

Zorg said:
I missed that completely. He would be hard pressed to find a place to plug it in.

I think that two Molex connectors are provided so that you can put them on different rails. Since I am sure that PSU only has a total of two rails and one of them is dedicated to the mobo, then you can use only one of the Molex connectors. Using both would be redundant.



Great advise, as alway. I would still opt to use both Molex connecter (One would work, as most molex on PSU are on the same rail). My reason is that it reduces the I squared R losses, using both connecters reduces the Current in each molex by halve. Very small advantage, but if available might as well use it.
December 1, 2007 9:15:43 PM

@Op -
You'll need to plug in both molex connectors - if you don't, you won't have enough juice going to the 6pin.
Normally, a molex has pin 1 suppling 12V, pin 4 is 5V and 2 and 3 are ground. 6pin pci-e has pins 1-3 suppling 12V and 4-6 are ground.
Its hard to tell from a picture, but the first duel molex to 6pin adaptor looks like its routing the 12V and ground from each to the 6pin (you don't need the 5V for the GPU card). You don't get all 3 12V lines since the molex can only supply two - but its probably enough for your card (check to see what kind of 12V amperage you need).
As for the rails - its a nice bonus if you can get the molex on seperate rails if you PSU supports that. But even if on one rail, you need both connectors so that you can get both 12V lines from each molex to the 6pin pci-e.

Later,
Sdrac

@delluser1: the later connector you showed only had one molex. I'd be careful trying to use that one as you could underpower the GPU.
December 1, 2007 10:34:25 PM

Wow im totally lost now.
Ok for once and for all.
I will buy that splitter that Delluser put, and a 3870 soon.
I will connect the molex into ONE 4pin connector from the psu since the splitter only has one.

Hopefully I won't have a bottleneck or have my psu and graphic card get nuked. If my psu goes will my card too?
a b U Graphics card
December 1, 2007 10:36:47 PM

It's a 66 watt card , how's it going to be underpowered by having an additional 25 watts from the molex connector along with the 75 watts provided by the PCIE slot ?
December 1, 2007 10:44:59 PM

At load I think it takes more than 66watts. Plus I overclock.
a b U Graphics card
December 1, 2007 11:28:04 PM

DellUser1 - You are correct in that they only route the +12/Gnd from the molex. However, as Zorg and I pointed out one could probably handle the current, as 70 W is only Approx 6A.

But he may need both depending on pinout on graphic card. On the card 6 pin the grounds are probably shorted together. The +12V pins on the graphics may not be connected. This would have to be verified by ohm meter. It's simpler to just use both molexs.
December 1, 2007 11:29:40 PM

@dell - I didn't know the wattage on the card was that low. If thats the case, then technically azn doesn't even need the 6pin connector (sans overclocking). At that wattage, I agree one molex would do the trick - but...

@azn - maybe I'm just the parnoid type, but if I'm spending the money on a new card I'd personally feel more comfortable playing it safe and use the dual connector.

Later,
Sdrac
a b U Graphics card
December 1, 2007 11:35:55 PM

RetiredChief said:
DellUser1 - You are correct in that they only route the +12/Gnd from the molex. However, as Zorg and I pointed out one could probably handle the current, as 70 W is only Approx 6A.

But he may need both depending on pinout on graphic card. On the card 6 pin the grounds are probably shorted together. The +12V pins on the graphics may not be connected. This would have to be verified by ohm meter. It's simpler to just use both molexs.


RC,
This is the same point I was making. There are plenty of people on the Dell forum who are using a Molex Y into a Molex to PCIE splitter, which equates to a single line. This is with an 8800 GT on the same psu.
a b U Graphics card
December 2, 2007 12:12:08 AM

Sorry DellUser1, I should have pointed toward SDRAC, Again sorry.

I just turned my computer off. demated the 6 pin. On My Graphics card the Gnds are shortted together as I figured. The +12 V are also shorted together on the card. Not sure if this is standardized and if it is then the molexs +12 power MUST come from one rail when using the "Y"
a b U Graphics card
December 2, 2007 12:17:02 AM

The correct answer has been written already, and I'd reitterate it except that the OP is so overwhelmed with wrong answers that he'd probably ignore any further advice.
December 2, 2007 1:27:48 AM

@crashman, would you please explain to the correct answer?

So most of the people here wants me to use the dual molex correct?
but the problem is, they don't have one at newegg. Unless somebody wants to show me one.
a b U Graphics card
December 2, 2007 1:31:56 AM

OK, the reason these adapters have two "Molex" connectors is that some cards need more power than one wire can provide. Each "Molex" has only one 12V wire, so the ideal solution is to use two separate power leads to power the two "Molex" connectors.

As I said, the "right" answer was already mentioned but appears to have been smothered by a flurry of haphazard answers.
December 2, 2007 2:07:24 AM

BUT the thing is I dont see any adapters with TWO molex connectors(not including the PCI).
Why can't you tell me what the right answer is. Mention the user or post number.
a b U Graphics card
December 2, 2007 2:40:51 AM

Fourth post from the top shows the 2-molex type adapter included with most graphics cards.
December 2, 2007 2:48:37 AM

Yes I know but I can't find them at newegg for separate retail. The 3870s don't seem to come with them.
a b U Graphics card
December 2, 2007 2:59:35 AM

go to google search "6 pin pci e to molex"

3 Company with 6 pin to 1 x4 molex$4 to $5
Note: also list a 6 pin to single molex at Newegg. You can read reviews.
Link to new egg
http://www.newegg.com/Product/Product.asp?Item=N82E1681...
Then select read all reviews

You will find several listing they are using with 1900xtx, one with 8800gtx. 1 said "NO Worky" messed up PSU (But psu may have been underpowered.

or enter 6 pin pci e to 2 x 4 molex
1 company $2 7", or $3 for 9"

My preference: 6 pin to 2 x 4 molex: however that said for your card
the single molex would work.

For Crashman - 22 ga wire (.025" Dia) will handle 7A which = 84 Watts
20 ga wire (.032" Dia) will handle 11A which = 132 Watts

Remember this is in addition to what is supplied by the motherboard

a b U Graphics card
December 2, 2007 3:03:04 AM

Remember, if companies thought a single 12V lead was enough they'd have put a "Molex" connector on the card, rather than come up with the PCI-Express power connector.
December 2, 2007 3:09:30 AM

Thanks chief. I'll go with the pci to 2 X 4 molex.
December 2, 2007 3:10:51 AM

Oh yeah and whats the difference b/w a 7" and 9"?
a b U Graphics card
December 2, 2007 3:19:37 AM

The lenght of the "Y" cable
a b U Graphics card
December 2, 2007 3:37:03 AM

Crashman - NOTE: the extra power connector for some graphic cards was a Floppy disk size connector. There are other consideration that come in to play in the choise of connector type such as a molex also has +5 which is not needed.

The bigger issue here is His PSU may be too small
a b U Graphics card
December 2, 2007 3:42:19 AM

Ah, how soon we forget: While most cards used a floppy-sized connector, a few used "Molex" sized connectors.
December 2, 2007 3:50:27 AM

@ retiredchief, I am pretty sure that my psu is not too small and im sure that it will work fine. If the 7" and 9" is about length then I think I'll get the 9" one just in case.
December 2, 2007 4:54:49 AM

I just got back a little while ago. I took a look at this, here is what I came up with. Crashman et al., feel free to let me know what you think.

First, OP just use the dual Molex to PCI and plug them both in if you have the Molex connectors available. Done.

The stock card draws about 105W. I don't know the split but assume it draws the full 66W of 12V from the motherboard. This leaves 39W or 39/12= 3.25 amps from the PCIe power connector. I looked at a dual 4 pin Molex to PCIe power adapter and the wire is 18 AWG (guage). Lets say that 18ga can handle 10A at that short length with room to spare. That leaves us with 6.75A or 200% headroom on a conservative 10A max. I don't think the wire will be catching on fire. As I said earlier, I believe the Molex connectors are split in order to put them on separate rails in order to not trigger the current limiter on any single rail. Since the OP has a dual rail and one rail is dedicated to the mobo, then he only has one rail left so there are no rails to split.

@OP, I looked at your setup and you require a 290W PSU at stock settings, so you are tight but you should be OK. If you OC you may find that you run into power problems. If so, and you figure it out before the PSU grenades, you might want to consider the Silencer 470 Dell Upgrade Power Supply as an upgrade.

Edit: I also removed an x1950pro and confirmed that the +12V are both common and all the GND are all common.

a b U Graphics card
December 2, 2007 5:37:20 AM

You're mostly good Zorg, except that all of a power supply's "Molex" connectors are connected to the same rail. The 6-pin PCI-E connector has that many pins so it can support three 12V wires...the adapter uses 2 12V wires...so I'd expect that the reason there are two 4-pin connectors is so that separate wires can be used.

But you're also right that his cards won't pull that much power.
December 2, 2007 6:14:46 AM

So you don't think the separate Molex connectors were provided with an eye to using separate rails on PSUs with more than two rails? Obviously on cards that are more power hungry than the 3870.
a b U Graphics card
December 2, 2007 10:33:40 AM

105 watts is claimed to be the " Max Power Draw " of the card, this leads to some confusion.
Example ; for over a year now the 8800 GTS has been said to be a 106 watt card, it is now being described as having a Max Power Draw of 147w. If you look at the power consumption charts on many of the reviews out there an 8800 GT based system draws about 45 watts less than an 8800 GTS based system.
So based on what I've been lead to believe for so long now a 3870 with a 105 watt max power draw ends up being about a 60 watt card.
The chart on the Atomic PC site calls it a 66 watt card.
http://www.atomicmpc.com.au/forums.asp?s=2&c=7&t=9354
So basically the extra power connection is there to take up the slack for powering the card when in 3D mode, but I don't think it will come close to it's "Max Power Draw" rating.
It is the same with an 8800 GTX, claimed to have a Max Power Draw of 177 watts, yet over the last year and a half all of the power charts show it as a 132 watt card. Dell used a PCIE power splitter in order to run the GTX with thier 375w psu, and we know that wont get you anymore power than the 75 watts that the PCIE connector can provide, it just gives the card connector power to prevent the low power warning from appearing.
Sorry for all the references to Nvidia cards, I'm not a fanboy, I've just been using them mostly, and I don't believe there's a difference in the way they consume power.
December 2, 2007 12:55:28 PM

Zorg said:
I just got back a little while ago. I took a look at this, here is what I came up with. Crashman et al., feel free to let me know what you think.

First, OP just use the dual Molex to PCI and plug them both in if you have the Molex connectors available. Done.

The stock card draws about 105W. I don't know the split but assume it draws the full 66W of 12V from the motherboard. This leaves 39W or 39/12= 3.25 amps from the PCIe power connector. I looked at a dual 4 pin Molex to PCIe power adapter and the wire is 18 AWG (guage). Lets say that 18ga can handle 10A at that short length with room to spare. That leaves us with 6.75A or 200% headroom on a conservative 10A max. I don't think the wire will be catching on fire. As I said earlier, I believe the Molex connectors are split in order to put them on separate rails in order to not trigger the current limiter on any single rail. Since the OP has a dual rail and one rail is dedicated to the mobo, then he only has one rail left so there are no rails to split.

@OP, I looked at your setup and you require a 290W PSU at stock settings, so you are tight but you should be OK. If you OC you may find that you run into power problems. If so, and you figure it out before the PSU grenades, you might want to consider the Silencer 470 Dell Upgrade Power Supply as an upgrade.

Edit: I also removed an x1950pro and confirmed that the +12V are both common and all the GND are all common.

I should be fine then because Dell under rates their powersupply. Im sure my psu can handle about 350 watts. I went to the website that calculate your power and it looks like I use around 277W but that was with a X1900XT.
Only thing im worried about is that, my psu will blow for no reason. I had to replace my psu with the warranty once already and my computer is only a year old.

The rails im guessing are connected by the 2 biggest psu connecter right?

Here at anandtech, they say that the 3870 draws 214 watts at load.
http://www.anandtech.com/video/showdoc.aspx?i=3151&p=11

@ Zorg
That psu seems a bit expensive for only 470 with 26amps.
I heard that dell computers, even though its on a BTX form can use ATX psu?
a b U Graphics card
December 2, 2007 3:32:00 PM

Zorg said:
So you don't think the separate Molex connectors were provided with an eye to using separate rails on PSUs with more than two rails? Obviously on cards that are more power hungry than the 3870.


Even on the latest power supplies, a PCI-E power connector gets all 3 wires from one rail. The split is meant to overcome per-cable limits, even though many cards draw too little power to worry about per-cable limits.
a b U Graphics card
December 2, 2007 4:49:53 PM

Zorg – I also confirmed (x1950xt) that the GPU shorts the Gnds
And the +12V. And Yes the molexs are on the same rail, in previous post

Crashman –If you noticed I RECOMMENDED/PREFERRED the split adaptor. Although I also said A single would work, and I stand By that.

Both of you have pointed out that the current requirements for the
3870 are well within the capabilities of a single Adaptor

Ga Ohms Max Max E loss @ 8A
2 ft I Load Pwr
18 .012 16A 192W .09V
20 .02 11A 132W .16V

Now for rationale why multiple wires are used and I would prefer the “Y”

(1) safety factor – Max Rail current (ie a short at the GPU) may, and
in most cases exceed the single wire. This in itself would not be a
problem as the PSU would shot down. The real problem would be
a partial short that could exceed wire max, but not +12 Rail max.

(2) E loss is for wire (doubled when adding pin contact Reistance). This could drop the +12 V on a marginal +12 V PSU (Say +11.75) to +11.5 Volts. E loss would be halved With a “Y” connector. Over time the contact resistance will Increase which could negate this advantage
December 2, 2007 9:39:21 PM

aznstriker92 said:
@ Zorg
That psu seems a bit expensive for only 470 with 26amps.
I heard that dell computers, even though its on a BTX form can use ATX psu?
Yes it is expensive but it fits the Dell case. I believe the form factor (physical size) of your Dell PSU is different, so you may have problems getting a standard PSU to fit. I'm not sure about that though, because I have never had a reason to research it. I have heard of people taking a Dremel to their case. That would be a possible option. Just be sure to check the size and rear layout of the PSU before you buy it.
December 2, 2007 9:51:24 PM

RetiredChief said:
Zorg – I also confirmed (x1950xt) that the GPU shorts the Gnds
And the +12V. And Yes the molexs are on the same rail, in previous post

Crashman –If you noticed I RECOMMENDED/PREFERRED the split adaptor. Although I also said A single would work, and I stand By that.

Both of you have pointed out that the current requirements for the
3870 are well within the capabilities of a single Adaptor

Ga Ohms Max Max E loss @ 8A
2 ft I Load Pwr
18 .012 16A 192W .09V
20 .02 11A 132W .16V

Now for rationale why multiple wires are used and I would prefer the “Y”

(1) safety factor – Max Rail current (ie a short at the GPU) may, and
in most cases exceed the single wire. This in itself would not be a
problem as the PSU would shot down. The real problem would be
a partial short that could exceed wire max, but not +12 Rail max.

(2) E loss is for wire (doubled when adding pin contact Reistance). This could drop the +12 V on a marginal +12 V PSU (Say +11.75) to +11.5 Volts. E loss would be halved With a “Y” connector. Over time the contact resistance will Increase which could negate this advantage
I'm with you on this, I don't see any way that the wires are going to burn under normal operation. I considered the voltage drop as being a concern and discounted that as the reason for making the Y cable, but it's possible. In order to have a problem you would have to have a weak PSU, so it should be replaced anyway.

@Crashman, I don't know what was in their minds when they came up with the PCIe or the Y connectors. As RetiredChief indicated overloading of the wiring is virtually impossible given normal conditions. Possibly a voltage drop problem if there is enough current, who knows. Maybe they are just over engineering, in order to be safe.

a b U Graphics card
December 2, 2007 10:41:10 PM

Zorg said:
Yes it is expensive but it fits the Dell case. I believe the form factor (physical size) of your Dell PSU is different, so you may have problems getting a standard PSU to fit. I'm not sure about that though, because I have never had a reason to research it. I have heard of people taking a Dremel to their case. That would be a possible option. Just be sure to check the size and rear layout of the PSU before you buy it.


Usually the Dell ATX power supplies are standard "PS/2" form factor, but many Dell, HP, and Compaq cases have an irregularly-shaped hole that requires the power line plug to be located in the same location as the original unit. What's worse, most power supplies have the plug on the "other" position (bottom rather than top) and power switches get in the way as well.

So, the only real way you can know if any particular standard unit fits is to look at the back of the case.
December 2, 2007 11:51:35 PM

Zorg said:
Yes it is expensive but it fits the Dell case. I believe the form factor (physical size) of your Dell PSU is different, so you may have problems getting a standard PSU to fit. I'm not sure about that though, because I have never had a reason to research it. I have heard of people taking a Dremel to their case. That would be a possible option. Just be sure to check the size and rear layout of the PSU before you buy it.

I've asked around and I believe it is possible to fit ATX psu's in my case.

EDIT:
Crashman, now that you talk about the plug hole, mine case does have the switch and the plug at the top of the case. So an ATX wouldnt work for me?
!