EVGA BQ850 Three 8-pin PCI-e plugs and three 6-pin plugs. Need 4 8-pins.

[EarthDog]

I get that ED, I however like to play on the cautious side. When more than 50% of your PSU is being dedicated to a single subsystem, you are going to want to balance.

I guess I have been lucky in all my years. Running a 295x2 (500W stock) with a heavily overclocked 5820K on a 750W PSU is one example. You may know something I dont here, but I could care less about balancing anything on single rail PSUs. It could care less if the CPU is sleeping and the GPUs are using 80% of the power. The only worry would be with a TRUE multi-rail PSU, which his is not, @ 70A on the 12V.

Im just not a proponent of over buying when you don't need to. Just waiting for something concrete with some kind of empirical testing to tell me otherwise. I expect more than specualtion from an EE!!!

 

[Blaylock]

To answer OP's original question directly. Since you have no plans to overclock these cards it's also safe to assume you will not be Modding them either....

I bought two AMD Vega 56 GPUs which requires two 8 pin connectors each. My EVGA BQ850 PSU has three 8-pin plugs and three 6 pin plugs. I have three remaining 6-pins that aren't being used from the single rail.

Yes you can alter one of the 2x6 pin cables to become an 8-pin. Each 6-pin will produce 75W of power while the 8-pin provides 150W each. Therefore if you convert the 2x6pin into a 1x8-pin you are producing no additional load on the PSU. DO NOT however create a 2x8-pin from teh 2x6-pin as you could overload the PSU.

 

[Xenohitsu]

To answer OP's original question directly. Since you have no plans to overclock these cards it's also safe to assume you will not be Modding them either....



Yes you can alter one of the 2x6 pin cables to become an 8-pin. Each 6-pin will produce 75W of power while the 8-pin provides 150W each. Therefore if you convert the 2x6pin into a 1x8-pin you are producing no additional load on the PSU. DO NOT however create a 2x8-pin from teh 2x6-pin as you could overload the PSU.

Thanks Blaylock. What I have on the EVGA PSU is two modular PSU 8-pin ports (labeled VGA 1 & 2 in image) that split into one 6+2 pin and one 6 pin each (Two 6+2 and two daisy 6 pins), plus another non-modular cable providing another 6+2 and a 6-pin. Therefore I am inquiring whether I can use any two of the three remaining 6-pins and turn them into an 8-pin, which the MSI Reference 56 Vega provides (a 6pin to 8-pin adapter). I will definitely not overclock and definitely not use one of the remaining 6pins to make 2 more 8-pins, just one since i only need one more to make 4 8-pins. https://www.newegg.com/Product/Product.aspx?Item=N82E16817438113

 

[Blaylock]

In that scenario I would say No. A 6+2 (8) pin + 6pin is 225W combined. Converting either of the daisied 6pin connectors could potentially draw 300W from a port only designed for 225W. Sorry for the confusion. You would need a different PSU for this to work.

 

[Xenohitsu]

In that scenario I would say No. A 6+2 (8) pin + 6pin is 225W combined. Converting either of the daisied 6pin connectors could potentially draw 300W from a port only designed for 225W. Sorry for the confusion. You would need a different PSU for this to work.

What if i took a 6 pin from one discrete port of the PSU (VGA 1) one and a 6-pin from the other discrete port (VGA2)? That is 75 watt each and would make 150. Again, the non-modular cable also includes a third 6-pin (plus a 6+2 already in use), thus if it balances better to source one 6-pin from there, I will do that. My original post indicated that, although I know it is a little convoluted.


Each Vega 56 card has two 8 pin ports, supporting up to 300 watts, but in practice it will draw around 200-230. The PSU can handle 840, and 600 towards two Vegas TDP excluding PCI-e draw, which won't be used when 300 is available from two 8 pins. The 6+2+ 6pin is 225 watts, and therefore one Vega 56 would use the remaining 6-pin from VGA1 and VGA2 using the Ebay-linked adapter, and the 6+2 pin from VGA 1 or 2 for each Vega. That is 225 watts per VGA port on the PSU, plus 225 watts from the non-modular cable providing another 225 watts (total 675watts) for the 4th 8-pin, of which only 150 would be used, or 225 and one of the VGA ports using only 150. Thus, 225+75 for one Vega, and 225+75 for the other Vega- one with an 6+2pin from VGA1 and a 2x6pin to 8pin adapter from VGA1+2 or non-mod cable, and the other Vega with one 6+2 pin plus the 6+2 pin from the non-mod cable.

In summary, Semi-modular Power supply:
VGA port 1: 6+2 +6 pin: 225 watts
VGA port 2: 6+2 +6 pin: 225 watts
Non-modular cable: 6+2 + 6 pin: 225 watts
Total: 675 watts available for PCI-express, 600 plugged in with three 6+2 pins and one dual female 6pin-to- male 8-pin adapter,

Not all 675 watts will be used of course- the motherboard needs around 125 for the CPU and SATA drives.

That would be around 740 watts on load if the motherboard uses around 35.


I'm looking at using one of these: http://www.ebay.com/itm/1PCS-PCI-E-...552547&hash=item33c9b8e2a5:g:~iEAAOSwCGVX~zcN

 

[EarthDog]

Rated and using are two different things...

 

[Sentential]

I get that ED, I however like to play on the cautious side. When more than 50% of your PSU is being dedicated to a single subsystem, you are going to want to balance.

And yes, not enough information is given by these posters. A lot of them are just general complaints with no background as to what caused their issue. It's always good to be aware of these issues as they can be the first part of diagnosing any future troubles someone may have.

Yea sadly with the cards being so hard to find getting good information about Vega has been a royal pain in the ***, thanks for the links. I know I'm not really helping a whole bunch given that I have a card and haven't gone into a whole lot of detail about the card; I just haven't had the time.

There are a lot of pages in that thread, but other users have mentioned issues. it could be just luck in the data set and each person has some other issue outside of drawing a ton from their sub 1K PSU.

However, the point is that if you plan on using these cards, make sure you don't skimp on the PSU. Its going to be stressed, and the more use these cards, the harder its going to be on the PSUs. 850W may work for now but will it last? Time will tell. Cards have only been out for a month or so.


BTWWW, news came in, 17.9.2 is coming in soon with Xfire support for Vega.

Yaaaaaaaasss That's great news!

 

[Xenohitsu]

Rated and using are two different things...

Yes, and maybe someone can help with this part. My PSU has two 8-pin ports that has each a cable with one 6+2 and one 6 pin. Are all 8-pin plugs ends-whether they plug into the PSU or the Video Card 150 watts? Or is the cable rated for more than 150 watts and somehow downconverts it to 150 watts on the Video card end's (8)/(6+2)pin end?

With that reasoning, I could understand that the PSU has two 8-pin ports rated for only 150 watts each, and one non-modular cable rated for 150 watts, even though all three cables each have one 6+2 pin and one 6 pin plug rated for 225 watts total perhaps only as an option for cards that need two six pins rather than one eight pin and one 6 pin... in "theory." Or is that in actuality?

 

[||Console||]

I find it funny for the last year ( @ least ) we have been telling people a quality 450-600w PSU is more than enough for a gaming system . Then Vega rolls out and its back to the monster PSUs of old =) .

I for one don't really care what the power draw is for any part of a system I own as long as it does what I want it to do , sure a lower power bill is nice but @ only 60$(max) a month to run my PC (I fold when not gaming) for the enjoyment I get from it is well worth it .

 

[Xenohitsu]

To answer OP's original question directly. Since you have no plans to overclock these cards it's also safe to assume you will not be Modding them either....



Yes you can alter one of the 2x6 pin cables to become an 8-pin. Each 6-pin will produce 75W of power while the 8-pin provides 150W each. Therefore if you convert the 2x6pin into a 1x8-pin you are producing no additional load on the PSU. DO NOT however create a 2x8-pin from teh 2x6-pin as you could overload the PSU.

My PSU has no 2x6 bundles in one cable. It only has 6+2 + 6 pins. Therefore uses either 150 watts per cable or 225, but i don't know enough about PSUs to answer that.

I am trying to make ONE 8-pin from 2 separate 6 pins (NOT from the same cable), NOT 2x8pins from 2x6pins.

The non-modular cable (not pictured) has a 3rd 6-pin (and a 6+2pin )that I'm asking if I can use as one of the 6-pins for the adapter.

 

[EarthDog]

I find it funny for the last year ( @ least ) we have been telling people a quality 450-600w PSU is more than enough for a gaming system . Then Vega rolls out and its back to the monster PSUs of old =) .

A single unmodified V64 and a 600W PSU IS still plenty.

 

[Blaylock]

Sorry for the delay Xeno. Sometimes we need to stop and think what the best solution is, not just what CAN be done.

In my opinion your best solution will be to pick up one of these bad boys.


2x4pin molex to 8pin GPU.

This will use the mostly unused molex cable and will keep from over drawing from any of the PSU ports.

If you've been in the game for a bit you should have one or two laying around. This one came with my HD7950 Vapor-X. Maybe your Vega came with one, I don't know. Either way you should be able to pick one up on the cheap and will eliminate the need to hack up your mod your cables.

EDIT: They come in Sata versions too if that works better for you. https://www.newegg.com/Product/Product.aspx?Item=N82E16812400105&Tpk=N82E16812400105

 

[Dolk]

Alright, let's hold up here. Blaylock, that may be a suggestion, but it's not a good one for this case. Those type of connectors are great for lower current GPUs. A molex rail is not rated to withstand the stress of a PCI-E driven rail.

Xen, let me point out some info that will help in this decision, but I will first and foremost say that you need to upgrade your PSU to something that supports your configuration out of the box. Doing these adapater/mix-match connection can easily overload a rail and hurt the PSU and potentially your cards.

In this post: "~" mean average

So let's learn, first documents:

EVGA 850W Manual
Wiki: PCI-E

We are all familiar with the fact that we can only pull a max of ~375W from PCI-E (connector adapter + power adapters). That means we can pull nearly ~30A per each GPU. Now for the most part, you will never see this unless you have a high end GPU like the Vegas. These cards have been reported to pull 220W just on power saving mode. I have personally recorded (via GPU-Z) my Vega 64 pulling 400W when unleashed. For the sake of this post, we will look at the V56 at 250W. Something easily obtainable doing mining and using the balanced/turbo mode in Wattman.

A V56 @250W is pulling ~21A.

The EVGA PSU is rated for 70A max out of BOTH PCI-E ports

2x V56 = ~42A pull. That gives you about 40% headroom on the PCI-E Rail, awesome. You should easily be able to satisfy these Vegas. No worries, but we need to connect them. For best current pulling capability, you should use a single cable with 2x8pin connectors. But you only have oneish... Well luckily you can call/email/pigeon carrier to EVGA and request an additional 2x8pin connector cable. You could also see if any sites sell additional cables that are compatible with your PSU.

Now scientific reasoning as to why you shouldn't use a single cable with 2x6pins and convert to 1x8pin and use your 1 cable with 3x8pins to connect all your V56's: The ground return path for one of your cards will be split and thus take longer. This can destabilize the card's ground plane as it is also sourcing into the ground of it's neighboring GPU. It's important not to do this because of load switch demands inducing large swings into non-coupled devices. This means that when one GPU starts to ramp up while another is ramping up (but behind the first), the first GPU can dump extra charge into the second and thus mess up some of the voltage sense circuits. These sort of things can cause damage or have adverse affects on performance. The degree of this is completely unknown and may not exist at all (this is theory practice as I've never experimented with a setup of this nature before). However, because there is a chance for this to cause harm, I reiterate my stance and suggest you get a second 2x8pin connector for your molex PSU.

 

[Xenohitsu]

Sorry for the delay Xeno. Sometimes we need to stop and think what the best solution is, not just what CAN be done.

In my opinion your best solution will be to pick up one of these bad boys.

View attachment 193609
2x4pin molex to 8pin GPU.

This will use the mostly unused molex cable and will keep from over drawing from any of the PSU ports.

If you've been in the game for a bit you should have one or two laying around. This one came with my HD7950 Vapor-X. Maybe your Vega came with one, I don't know. Either way you should be able to pick one up on the cheap and will eliminate the need to hack up your mod your cables.

EDIT: They come in Sata versions too if that works better for you. https://www.newegg.com/Product/Product.aspx?Item=N82E16812400105&Tpk=N82E16812400105

I have seen these, but only in the 6-pin variety. Will definitely consider.

 

[Blaylock]

Dolk I think you may have misread his post. He current has zero 2x8 pin connectors. His PSU comes with one hard wired 6+2 with a daisied 6 pin and 2 modular 6+2 with a daisied 6 pin. Again each vga port on his psu is only rated for 225W (150W + 75W). Ordering a 2x8 pin for this PSU risks overloading.

A molex rail is not rated to withstand the stress of a PCI-E driven rail.

Are you suggesting his port for the Molex connectors isn't rated for 150W?(1x8 pin) That seems questionable. Also IIRC this is a single rail Unit.

Edit: I just checked my unit for verification. I have the GQ series not the BQ and this one comes with 2x6+2 pin connectors. Xeno it would be in your best interest to contact EVGA and confirm if the ports are rated for 225W or 300W. If they are 300W rated than Dolks suggestion of getting a 2x8pin (or 2 honestly) would be ideal. If they are only rated to 225W then obviously you will either need the adapter i posted or consider a better equiped PSU.

 

[Xenohitsu]

Dolk I think you may have misread his post. He current has zero 2x8 pin connectors. His PSU comes with one hard wired 6+2 with a daisied 6 pin and 2 modular 6+2 with a daisied 6 pin. Again each vga port on his psu is only rated for 225W (150W + 75W). Ordering a 2x8 pin for this PSU risks overloading.



Are you suggesting his port for the Molex connectors isn't rated for 150W?(1x8 pin) That seems questionable. Also IIRC this is a single rail Unit.

Edit: I just checked my unit for verification. I have the GQ series not the BQ and this one comes with 2x6+2 pin connectors. Xeno it would be in your best interest to contact EVGA and confirm if the ports are rated for 225W or 300W. If they are 300W rated than Dolks suggestion of getting a 2x8pin (or 2 honestly) would be ideal. If they are only rated to 225W then obviously you will either need the adapter i posted or consider a better equiped PSU.

Thanks Blaylock, I will contact EVGA to ask about the PCI-e port being 225 or 300. That will make it easier to find out if an adapter from the non modular cable would be better. I figure VGA 1 and 2 could be used as two PCI-e pins for one Vega, and the non modular one plus a molex or sata adapter as the third, unless the nonmodular cable is rated for more than 225, I'll ask for two 2x8 pin adapters..

 

[Dolk]

Ok yes, I didn't realize that, and the product description listed 3x8pin connectors, but didn't specify how they were setup.

If you look at the molex or pref output for the molex connectors, you'll see that they are rated for a max current output of 20A. Lower than the ~21A @250W that we are predicting the cards to run at. You would be OCPing that rail all day if you used that configuration.

I also agree with Blaylock to contact EVGA and see what they suggest.

 

[Xenohitsu]

Ok yes, I didn't realize that, and the product description listed 3x8pin connectors, but didn't specify how they were setup.

If you look at the molex or pref output for the molex connectors, you'll see that they are rated for a max current output of 20A. Lower than the ~21A @250W that we are predicting the cards to run at. You would be OCPing that rail all day if you used that configuration.

I also agree with Blaylock to contact EVGA and see what they suggest.

I contacted EVGA and they were very nice. They offered to mail two 8-pin adapters at no charge. They did not recommend 3rd party adapters. I did ask to confirm if they were in fact two 2x8 pins, but I am waiting on that response. It seems like it would- my Seasonic M12II 620w has one or two modular 2(6+2) pin adapter. Interestingly, the Seasonic supports 24Amps on each 12V1 & 12V2 rail, which may be enough to run it on BIOS2 (200w). I hadn't realized I had Seasonic 2x8pin but I am hesitant to use it on the EVGA considering their official response. Plus I need two EVGA branded ones anyways. Thanks EVGA!

 

[Xenohitsu]

some interesting updates on the branding name of Crossfire being changed to "mGPU" in DirectX 12: http://wccftech.com/amd-bids-farewell-to-crossfire-mgpu/

 

[Blaylock]

I contacted EVGA and they were very nice. They offered to mail two 8-pin adapters at no charge. They did not recommend 3rd party adapters. I did ask to confirm if they were in fact two 2x8 pins, but I am waiting on that response. It seems like it would- my Seasonic M12II 620w has one or two modular 2(6+2) pin adapter. Interestingly, the Seasonic supports 24Amps on each 12V1 & 12V2 rail, which may be enough to run it on BIOS2 (200w). I hadn't realized I had Seasonic 2x8pin but I am hesitant to use it on the EVGA considering their official response. Plus I need two EVGA branded ones anyways. Thanks EVGA!

Excellent news Xeno! They will likely send you 1 or 2 of their 2x6+2 cables. This is what comes with the 850 GQ. I would not use a Seasonic (or any other brand)cable with an EVGA PSU as the ports pin-outs are likely different per manufacturer.