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PCI-e power connectors according to Coolermaster

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  • Graphics Cards
  • Cooler Master
  • Cable
  • PCI Express
  • Graphics
Last response: in Graphics & Displays
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August 18, 2012 12:12:55 AM

This can't be right?! If I take this literally, even 3 cables from the PSU (each with a 6 and 6+2 connector) would not be enough for SLI/Crossfire

(From a FAQ on their site)

"Question
Can I use the two PCI-e connectors on the same cable at the same time?

Answer
No, please be noticed that it will be better to use one PCI-e connector on each cable for best performance. If you need two, it is suggested to use the connectors on different cable.
"

If they did not mean for you to use both, why a 6 AND a 6+2? Maybe this is true for some PSUs?


More about : pci power connectors coolermaster

Anonymous
a c 117 U Graphics card
August 18, 2012 12:17:49 AM

without doing coolermaster's thinking:
they are less than desirable PSUs; whatever configuration they had in mind with having a 6 and 6+2 pin power connectors on the same cable is beyond me and should be avoided.
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a c 122 U Graphics card
August 18, 2012 12:31:35 AM

Each 6 pin PCIe connector is rated to deliver 75 watts of power and consists of 2 or 3 +12 volt wires and 3 ground wires. One of the 3 +12 volt connections may be left unpopulated which results in only 5 wires being present.

Each 8 pin PCIe connector is rated to deliver 150 watts of power and consists of 3 +12 volt wires and 5 ground wires. All wires should be populated.

It is common for manufacturers of high quality PSUs to use only 6+2 pin connectors where the +2 pins can be separated. This allows for the same connector to be used for both 6 and 8 pin PCIe connections. Note that since the 2 separable pins are ground wires the entire assembly must be able to deliver 150 watts of power on each of the 6+2 assemblies regardless of whether they are used as 6 pin adapters or 8 pin adapters.

Some cables that have both 6 pin and 8 pin adapters on the same cable are usually only rated to deliver 150 watts of power over the 8 pin adapter. They are not rated to deliver 225 watts of power; either-or, not both.

Using PCIe cable splitters is usually ill-advised.

While it is not within the ATX specification to take an 8 pin connector and split it into two 6 pin connectors this is safe on almost any high end PSU. Each 6 pin delivers half of an 8 pin and the 8 pin cables should be able to handle it just fine.

It is not safe to take a 6 pin PCIe connector and split it into two 6 pin PCIe connectors and it is not safe to join two Molex connectors into a single 6 pin PCIe connector.
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August 18, 2012 12:34:39 AM

Just to clarify, hard to tell the exact wiring because it's shrouded. For all I know it TWO sets of wires in the same shroud. Obviously if the one set of wires is connected to the other at the end of the run it defeats the purpose of running so many 12v and ground leads for pcie
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August 18, 2012 12:35:56 AM

Note that if that FAQ Did apply...the psu would fail for ski or xfire because I would need 4 cables form the psu and there are only 3. They claim xfire cert whatever that might be which implies you would be able to do xfire and contradicts the faq
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a c 122 U Graphics card
August 18, 2012 12:37:56 AM

michaeljhuman said:
Just to clarify, hard to tell the exact wiring because it's shrouded. For all I know it TWO sets of wires in the same shroud. Obviously if the one set of wires is connected to the other at the end of the run it defeats the purpose of running so many 12v and ground leads for pcie


I really have to agree with Looniam on this, having both a 6 pin and an 8 pin on the same cable is nonsensical when it's easier to just have a single 6+2 connector. It seems to me like the person who wrote that FAQ and/or the person who designed their power supplies may have undergone an icepick lobotomy.
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a c 122 U Graphics card
August 18, 2012 12:40:02 AM

michaeljhuman said:
I did confirm, indeed one connector is bridged to the other. Either that works, is the psu is not suitable for xfire and sli. I do understand the. Power limitations mentioned above if the two connectors share the 12v and ground leads


Which model PSU do you have?
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August 18, 2012 12:41:23 AM

I did confirm, indeed one connector is bridged to the other. Either that works, is the psu is not suitable for xfire and sli. I do understand the. Power limitations mentioned above if the two connectors share the 12v and ground leads
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a c 291 U Graphics card
August 18, 2012 12:43:07 AM

I'm pretty sure that they meant that you shouldn't use splitters for one 6-pin to two 6-pin ones.
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August 18, 2012 12:47:30 AM

Hardware secrets review the psu and noted the same common issue. So is the coolermaster cya? Give you what looks like a psu for 3 cards, but it would only do one if you followed their FAQ...shady? Next time will get the corsair maybe.
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August 18, 2012 12:48:03 AM

Oh sorry coolermaster 800 silent gold
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August 18, 2012 12:49:52 AM

What I can do, is to hook up the 3rd cable to power the first card. Disable xfire and rerun the dirt 3 bench to see if it's power starved. Will repost if I do
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Anonymous
a c 117 U Graphics card
August 18, 2012 12:50:50 AM

again, coolermaster has a less than stellar reputation. many PSU makers will place a large amount of amperage on the 3.3 and 5 volt rails (which don't get used much anmore) to embellish the rated total wattage of the PSU.

for whatever reason that was behind that configuration really doesn't matter; it is a horrible design. consider each PCI-E power cable of being able to deliver 150 watts using the 6+2 pin maximum.

edit:
after giving the PSU a look
the rated 12 volt rail would not be correct for a PSU that size 65 amps which is 780 watts. it would be more appropritate that the 12 volt rail deliver 80% of the total rated wattage which is 640 watts or 53 amps.consider for safety of the system to reserve 13 amps for the cpu, hard drives, ram, chipset and such so thats 40 amps of availible 12 volts for the 3 pci-e power connection cables.

divide by 3 for each cable and that would be 13.3 amps or 160 watts for each pci-e power cable or enough for one 6+2 pin only

now if you have 2 grfx cards that each need a 6 and 6+2 power connections. use the two 6+2 and one 6 pin connection from the cables. and then a molex to 6 pin connection for the other.
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a c 122 U Graphics card
August 18, 2012 1:12:53 AM

Anonymous said:
again, coolermaster has a less than stellar reputation. many PSU makers will place a large amount of amperage on the 3.3 and 5 volt rails (which don't get used much anmore) to embellish the rated total wattage of the PSU.

for whatever reason that was behind that configuration really doesn't matter; it is a horrible design. consider each PCI-E power cable of being able to deliver 150 watts using the 6+2 pin maximum.

edit:
after giving the PSU a look
the rated 12 volt rail would not be correct for a PSU that size 65 amps which is 780 watts. it would be more appropritate that the 12 volt rail deliver 80% of the total rated wattage which is 640 watts or 53 amps.consider for safety of the system to reserve 13 amps for the cpu, hard drives, ram, chipset and such so thats 40 amps of availible 12 volts for the 3 pci-e power connection cables.

divide by 3 for each cable and that would be 13.3 amps or 160 watts for each pci-e power cable or enough for one 6+2 pin only

now if you have 2 grfx cards that each need a 6 and 6+2 power connections. use the two 6+2 and one 6 pin connection from the cables. and then a molex to 6 pin connection for the other.


I read over the detailed hardwaresecrets review and they indicated that it can safely deliver over 900 watts without leaving specification so the 65A on the 12 volt rail isn't unrealistic.

I still wouldn't trust it as much as I would trust a Corsair HX850/AX850 or Seasonic X-850 (Seasonic also manufactures the TX850/AX850 so they're basically all the same PSU).
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August 18, 2012 1:13:22 AM

Well you know how it is. Maybe I did not buy the best supply for the money, but after testing one card with two different power cables to it, I saw no fps difference.

So maybe it's fine, even though it's not theoretically good.

In retrospect, there were probably better supplies. But when you price out a PC, you have a lot to consider, and I did not know 2 months ago what I know now about such things.

Always interesting for me to learn as much as possible about everything I dip my toes into, so this was educational. I do feel Coolermaster is a bit confused by claiming crossfire compatibility, which is simply not possible if you also tried to follow their one connector per cable theory.

My guess is that I don't need 150 watts per connector, so there's no issue. Maybe overclocking suffers, as I don't have the metrics needed to test the single card with both cables vs one cable with stock vs OC.

Thanks
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Anonymous
a c 117 U Graphics card
August 18, 2012 1:17:21 AM

Pinhedd said:
I read over the detailed hardwaresecrets review and they indicated that it can safely deliver over 900 watts without leaving specification so the 65A on the 12 volt rail isn't unrealistic.

I still wouldn't trust it as much as I would trust a Corsair HX850/AX850 or Seasonic X-850 (Seasonic also manufactures the TX850/AX850 so they're basically all the same PSU).

and did you see those ripple results?
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a c 122 U Graphics card
August 18, 2012 1:17:31 AM

michaeljhuman said:
Well you know how it is. Maybe I did not buy the best supply for the money, but after testing one card with two different power cables to it, I saw no fps difference.

So maybe it's fine, even though it's not theoretically good.

In retrospect, there were probably better supplies. But when you price out a PC, you have a lot to consider, and I did not know 2 months ago what I know now about such things.

Thanks


Power delivery won't affect the FPS at all. It will affect whether or not the card runs stably. A knockoff PSU is like playing Russian Roulette with a magazine loading pistol. A poor quality PSU will simply cause the system to crash under heavy loads. A moderate quality PSU won't allow users to exploit overclocking headroom and may die out after a few years. A good quality PSU will last a long time and never give you any stability issues.
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August 18, 2012 1:19:33 AM

Ok, well, if so, I have no way to prove this supply is inferior without having another supply to compare it to :) 

Will just have to live with it.

I can overlock to nearly 6970 specs, but it runs stupid hot, so I have to frame limit it via vsync anyway.

I am replacing the dual 6950 with GTX cards due next week. We will see how that works.

Certainly happy for opinions, but I have already spent a ton on this build, what with the two GTX cards and the two 6950 cards I will have to sell at a loss. Hoping to NOT have to spend more; I am sure you can see that :) 
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a c 122 U Graphics card
August 18, 2012 1:22:05 AM

Anonymous said:
and did you see those ripple results?


Yeah I did. 112mv from one reviewing outlet and around 95mv from another. Not terrific but within specification. The -12 volt rail was out of spec but that's not a huge deal. Even when it was running upwards of 900 watts DC output it was still within the ATX specification on the 12 volt rail. There are a lot of PSUs which can't even operate at 100% load much less at 100% load within the ATX specification.

It's a weak link for sure but it probably won't affect the OP.
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a c 122 U Graphics card
August 18, 2012 1:23:20 AM

michaeljhuman said:
Ok, well, if so, I have no way to prove this supply is inferior without having another supply to compare it to :) 

Will just have to live with it.

I can overlock to nearly 6970 specs, but it runs stupid hot, so I have to frame limit it via vsync anyway.

I am replacing the dual 6950 with GTX cards due next week. We will see how that works.


Keep in mind that each GPU can draw 75 watts from the PCIe socket alone (150 watts on 2.0 and 3.0 gen but most don't exploit this) so you'd probably be okay running each card as I don't expect that each one will draw much more than 150 watts from both PCIe power cables combined. Just don't run dual 690s
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Anonymous
a c 117 U Graphics card
August 18, 2012 1:25:47 AM

michaeljhuman said:
Ok, well, if so, I have no way to prove this supply is inferior without having another supply to compare it to :) 

Will just have to live with it.

I can overlock to nearly 6970 specs, but it runs stupid hot, so I have to frame limit it via vsync anyway.

I am replacing the dual 6950 with GTX cards due next week. We will see how that works.

Certainly happy for opinions, but I have already spent a ton on this build, what with the two GTX cards and the two 6950 cards I will have to sell at a loss. Hoping to NOT have to spend more; I am sure you can see that :) 

without trying to sound like a jerkface; you asked about using two connectors on the same power cable; which is a no. but you did not ask if you could use the PSU for a muti card configuration; which is possible but would need a molex to 6 pin adapter.
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August 18, 2012 1:40:56 AM

Understood that I could use molex power, thanks. Just realize that the PSU is advertised as SLI/Crossfire certified, hence my attempts to understand how that is supposed to work without the need for power from additional non PCI-e connectors.

If that (expecting the user to hook up more wires using adapters) was the plan, the engineers and marketers should be shot - the engineers for building such a monstrosity and the the marketers for not putting this bizarre wiring scheme into a manual.

<shrug>

It does seem to work until proven otherwise, so I will limp along without molex to PCI-e power if possible :) 

Working as a software engineer, I know stuff goes horribly wrong sometimes. Maybe this is one of those cases, I could not say.




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a b U Graphics card
August 18, 2012 1:13:35 PM


michaeljhuman said:

It does seem to work until proven otherwise

Funny thread
It does work, that's why the engineers are designing them that way

GTX480 Quad SLI , dual pcie connector cables
http://www.youtube.com/watch?v=7V13ZGIZgYYGTX 480 Quad SLI

Quite a few highly rated psu's use the same configuration ( even some lower budget units, my GTX570 has no issues running on an Antec NE520 with it's dual connector cable )


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Anonymous
a c 117 U Graphics card
August 18, 2012 5:14:38 PM

delluser1 said:
Funny thread
It does work, that's why the engineers are designing them that way

GTX480 Quad SLI , dual pcie connector cables
http://www.youtube.com/watch?v=7V13ZGIZgYYGTX 480 Quad SLI

Quite a few highly rated psu's use the same configuration ( even some lower budget units, my GTX570 has no issues running on an Antec NE520 with it's dual connector cable )

since i know you know a lot better than i, i'll rescind my advice @ avoid using both connections.

yeah it is funny watching a chicken run around with its head cut off.
[:pdxalex:1]
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