4x 6pin pcie = 4x 8pin pcie? evga Geforce 770 4gb classified + alienware x51

[fubusama]

hi all,

I just upgraded the video cards from my alienware x51 (2010) from 2x radeon 1gb cards to 2x evga geforce 770 4gb classified. But I'm having some problems powering both cards at the same time. Both cards require 2x 8pin pci-e to power it up.

I believe my power supply is 1000w/1100w, but that is just based on research. I can't actually see anything on the label itself.

The power supply has 4x 6pin PCIe cables, and 2 of them have dangling +2 pins. I'm not sure about any rails or anything like that.

The video cards came with two 2x 6pin -> 1x 8pin adapters. So I setup all 4 of my 6pin pci cables to 2 8pin to power a single video card. Now the 2nd one has no power.

It also appears that I have a free 8pin cable from the power supply, not sure if it is for the CPU or not? the cable is very short...

So my questions are:

1. Since i have 4x 6pin pcie, can I just buy 4 6pin->8pin adapters?
2. If #1 is no good, should i consider doing some molex to pci adapters? I don't need my cd drive and I think there are some extra ones for the HDD

Sorry I am very n00b at this stuff. Please help!

 

[geofelt]

Exactly what make/model psu do you have?
The wattage is not as important as the +12v amps.

Two GTX770 classified require serious power. Two 8 pin connectors are 300w plus the 75w for the slot gives you the need for 750w for the cards alone.
That should be no problem for a quality 1000w psu.

If your psu has 2 6+2 cables and 2 6 pin cables, that is not enough.
If your psu were capable of more, they would have been included.

Adding molex to 6 or 8 pin adapters will do the connection, but if the psu is not capable it will not run properly.
Moreover, If your psu is a cheap one that lacks protective circuitry, it may damage everything if it fails while overloaded.

I suggest you use only one card until you get this sorted out.

 

[Thelps]

What model of PSU are you running?

Is your PSU modular? Can you remove the cables from the PSU itself? If so it might just be a matter of purchasing some 8-Pin PCI-E x16 cables.

 

[fubusama]

I will try to figure out the PSU model, unfortunately I don't know. I know it's stock that came with my alienware PC, and it is a minimum of 1000w. My PSU is not modular.

I have seen a lot of threads saying that it's safe to use a 6pin -> 8pin pcie adapter, but i'm nervous about using 4 of them! (or I guess i could use 2 since I have 2 6+2s already)

 

[Thelps]

I will try to figure out the PSU model, unfortunately I don't know. I know it's stock that came with my alienware PC, and it is a minimum of 1000w. My PSU is not modular.

I have seen a lot of threads saying that it's safe to use a 6pin -> 8pin pcie adapter, but i'm nervous about using 4 of them! (or I guess i could use 2 since I have 2 6+2s already)

If you can get the model number of your PC (most likely on a label on the back of the case) that will let you use a search engine to determine the exact specifications of your machine.

Alternatively, the instruction manual included with the computer should provide a list of parts in the PC.

Ultimately, Geofelt is correct in that it's a risky business playing with a PSU's outputs. Decide whether to attempt a converted connection or invest in a different PSU.

 

[fubusama]

The PSU says it is Alienware 1100Watt Multi-GPU Approved. Does that help at all?

 

[fubusama]

Found the owner manual for my PC -> ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_alienware_dsk/alienware-area51_Owner%27s%20Manual_en-us.pdf Still doesn't give exact model.

I'm happy to upgrade the PSU if it's required. But 1100w seems like it should be enough?

 

[Thelps]

Found the owner manual for my PC -> ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_alienware_dsk/alienware-area51_Owner%27s%20Manual_en-us.pdf Still doesn't give exact model.

I'm happy to upgrade the PSU if it's required. But 1100w seems like it should be enough?

That's certainly a sufficient wattage for the task you're contemplating.

I can't give a definite answer but it's worth a try if you're willing to shoulder the (admittedly small) risk.

 

[fubusama]

Found the owner manual for my PC -> ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_alienware_dsk/alienware-area51_Owner%27s%20Manual_en-us.pdf Still doesn't give exact model.

I'm happy to upgrade the PSU if it's required. But 1100w seems like it should be enough?

That's certainly a sufficient wattage for the task you're contemplating.

I can't give a definite answer but it's worth a try if you're willing to shoulder the (admittedly small) risk.

so how should I do it without the connectors? Just use adapters to convert my 2 6 pins into 8 pins, then use my "stock" 6+2s for the other 2 8pin i need?

 

[Thelps]

I'd say give the pin hack a try. If it doesn't work then you're looking at buying a new PSU to support two cards. Get a modular one if you get the chance. It'll help stop this problem recurring.

You may want to PM are a 'Master' PSU guru first though. Just to ensure you're not going to fry anything with the pin hack.

 

[hunter315]

Luckily, being a big OEM, Dell gets all of their power supplies 80+ rated so we can actually learn more about your supply from Ecova than we can from dell, if its 1100W and from 2010 then it has to be one of these two
N1100EF-00
H1100EF-00
And google images gets us the labels, both of them spec that you have 1000W between the 12V rails which gives you 83A to play with
http://www.stuartconnections.com/de/power-supplies/3181-Dell-Precision-T7500-1100W-Power-Supply-Unit-PSU-H1100EF00-W301G.html

http://www.stuartconnections.com/de/power-supplies/2565-Dell-Precision-T7500-Alienware-Area-51-ALX-1100-Watt-PSU-Power-Supply-R622G-N1100EF00.html

Guru3d measured a peak load of 505W at the wall with a pair of 770s loaded up so the cards are only using ~200W, it seems like they gave them 2 8 pin connectors so there wouldn't be a question about if they had enough power not because they actually need 300W for the card, so you can use the 2 6+2 and 2 6=>8 pin adapters and be fine
http://www.guru3d.com/articles_pages/geforce_gtx_770_sli_review,4.html

Your PSU is plenty strong for those cards, which is a good thing given that it is a non-standard form factor so you don't really have any replacement options.

 

[Thelps]

Luckily, being a big OEM, Dell gets all of their power supplies 80+ rated so we can actually learn more about your supply from Ecova than we can from dell, if its 1100W and from 2010 then it has to be one of these two
N1100EF-00
H1100EF-00
And google images gets us the labels, both of them spec that you have 1000W between the 12V rails which gives you 83A to play with
http://www.stuartconnections.com/de/power-supplies/3181-Dell-Precision-T7500-1100W-Power-Supply-Unit-PSU-H1100EF00-W301G.html

http://www.stuartconnections.com/de/power-supplies/2565-Dell-Precision-T7500-Alienware-Area-51-ALX-1100-Watt-PSU-Power-Supply-R622G-N1100EF00.html

Guru3d measured a peak load of 505W at the wall with a pair of 770s loaded up so the cards are only using ~200W, it seems like they gave them 2 8 pin connectors so there wouldn't be a question about if they had enough power not because they actually need 300W for the card, so you can use the 2 6+2 and 2 6=>8 pin adapters and be fine
http://www.guru3d.com/articles_pages/geforce_gtx_770_sli_review,4.html

Your PSU is plenty strong for those cards, which is a good thing given that it is a non-standard form factor so you don't really have any replacement options.

+1 that. ^^

 

[fubusama]

Your PSU is plenty strong for those cards, which is a good thing given that it is a non-standard form factor so you don't really have any replacement options.

You are the best. Thank you so much!

So I bought the two adapters, tried to go as high quality as i could. Setup each card with a 6+2pin pcie and a 6pin pcie->8pin pcie. Everything powered up, all my games run great. I can watch movies on one screen while playing games at 60fps on the other... so practically it's working amazing.

But... I ran a FurMark benchmark test and the PC just shuts off before it finishes... Guess that means my PSU isn't strong enough afterall? Or maybe despite going expensive with the adapters, they are bad?

 

[hunter315]

Well start by ruling out a bad card or overheating first, it seems like they work under normal situations but fail under extreme testing so be a bit scientific about this and you can figure it out pretty quickly.

If you disable SLI and run furmark does it crash out? If you swap to the other card does it work as well? That'll prove that neither individual card is causing the issue.

Second, get something like MSI afterburner to monitor all the temps and other bits, and rather than running the furmark benchmark, do the stability test and dial up the load manually, run it windowed at the next resolution below your native resolution without any AA, see what the temps get up to and if you crash out, then add AA, check temps again, up the resolution without AA, check temps. This lets you figure out how hot your cards get as their workload increases, the Xtreme Burning Mode in FurMark is super unrealistic so never use that, you'll find a card pulling ~20% more power than normal because its a workload designed to max out cards.

If you fail the first set of tests its a bad card, if you have reasonable temps on the second set and only crash out when you get to really high resolution+AA+Xtreme Burning Mode then its likely power but you will also be drawing far more than any normal circumstance would lead to.

 

[fubusama]

Hey, so I tried a bunch of stuff and was able to get it stable for furmark benchmarks by underclocking it to 90% max power. Pretty happy with that.

 

[hunter315]

So it seems like the extreme nature of furmark is what is causing you issues, not surprising since both AMD and nVidia have been recommending against using furmark on their cards and some models automatically kick back when something like FurMark or OCCT is loaded up onto them.

You seem to be able to play games fine according to an earlier post and that seems like the goal so i think you are good to go, its just that non-standard usage results in non-standard behavior(shocker!) but i wouldn't worry too much about that.