Video Card (RX 480) Power Draw from a Server PCIe slot (25W limit!!!) ?

[petreza]

I have a PowerColor RX480 on order which I plan to put in a Dell R810 2U server. The power supplies in the server do not have spare power outputs so I am going to use an external PSU just for the video card.
With all the talk about the RX480 exceeding the power draw limit of the PCIe slots I decided to check what that limit is for my specific server. I was surprised to find that it is only 25W! In the Dell Technical Guide it says this limitation is due to thermal constraints which are not applicable in my case - the system is water cooled and the lid is off. Here is the link:

p. 39 - paragraph that starts with "Each slot..."

http://i.dell.com/sites/doccontent/...cuments/poweredge-r810-technical-guide-en.pdf

I plan to plug the card in the top slot of the riser card that has only 2 slots (Riser2) and I do not plan to plug anything in the bottom slot ( or maybe just a USB card ). So the riser card should have at least 50W available.

Do you think I am risking frying the motherboard or the riser card if I do this?
If so, what if I use one of these:

Amazon.com: 16X PCI-Express PCI-E 164 Pin Ribbon Powered Riser Extender Cable: Electronics

Thanks in advance for any advise or comment!

 

[NKD]

I would wait until the update tomorrow. we will all find out. But the server seems like its not designed for anything even lowest of the mid range cards. 25w? Man thats low!

 

[petreza]

I would wait until the update tomorrow. we will all find out. But the server seems like its not designed for anything even lowest of the mid range cards. 25w? Man thats low!

Well, they say it is for thermal reasons - 2 cards 25W each + 4 cards 15W each = 110W ; electrically it might have a wider margin.
Keep in mind that the 4 processors have a theoretical max of 520W so it adds up. But the fans at MAX were so strong (before I removed them) that I would have guessed they can easily dissipate 2000W. But what do I know.

I will wait and not plug anything until I have more info.

Meanwhile I found a 16x PCIe powered riser card for cheap and local (US shipping) so I will order one just to have it:

Powered PCI-E 16X to 16X Adapter Riser Extension Cable Molex Power Connector

What is happening tomorrow - is AMD releasing a driver update addressing the issue?

 

[petreza]

The max power draw from the PCIe happens only when under a heavy load, right?
I should not have power issues for just desktop (4K) use?
How about during boot?
(I know that CPUs can draw a lot of power when booting but that is not applicable to GPUs, right?)

 

[primetime]

Well, they say it is for thermal reasons - 2 cards 25W each + 4 cards 15W each = 110W ; electrically it might have a wider margin.
Keep in mind that the 4 processors have a theoretical max of 520W so it adds up. But the fans at MAX were so strong (before I removed them) that I would have guessed they can easily dissipate 2000W. But what do I know.

I will wait and not plug anything until I have more info.

Meanwhile I found a 16x PCIe powered riser card for cheap and local (US shipping) so I will order one just to have it:

Powered PCI-E 16X to 16X Adapter Riser Extension Cable Molex Power Connector

What is happening tomorrow - is AMD releasing a driver update addressing the issue?

driver and or bios.....well see tomorrow. The driver team has been working OT thru the weekend on a power fix

 

[primetime]

The max power draw from the PCIe happens only when under a heavy load, right?
I should not have power issues for just desktop (4K) use?
How about during boot?
(I know that CPUs can draw a lot of power when booting but that is not applicable to GPUs, right?)

I think you be ok for booting up or general use. All the known overload issues so far has been under heavy game use

 

[Nenu]

Well, they say it is for thermal reasons - ...

That cant be the whole story.

If there is only one power connection leaf in the PCI-E slot and you try to put more than 25W through it, it will start getting hot.
I suspect this is the reason, the limit on current capacity.

If there are more leaf connections, 50% more current wouldnt cause a heat issue, it would function very close to a wire.
Unless they really cheaped out and there is very little spring contact or the leaf connections are super thin.

Regardless, something isnt up to spec, I wouldnt push it.
The 480 has been demonstrated to exceed 75W on that power connection.

ps
chaps, he wouldnt be purchasing this card to only run a desktop, that would be daft.
It will be put under load.

but op, if you really dont intend on utilising the power of this card, get something safer and cheaper.

 

[Trimlock]

Why get the card if it's only going to idle?

 

[thesmokingman]

If you read the pcper test, they consulted mb makers and confirmed with them the traces can handle high load and the weakest point for failure would be the pins. That said true server gear is built to handle full load 24/7.

 

[Nenu]

If you read the pcper test, they consulted mb makers and confirmed with them the traces can handle high load and the weakest point for failure would be the pins. That said true server gear is built to handle full load 24/7.

The pins are the leaf connections.

Full load does not define the load.
A pin designed to take a load, can take that load, as long as it is a good connection.

 

[Trimlock]

If you read the pcper test, they consulted mb makers and confirmed with them the traces can handle high load and the weakest point for failure would be the pins. That said true server gear is built to handle full load 24/7.

MB designers can change the power environment if they want to, in the case of a server they'd do it to reduce the power footprint.

 

[noko]

Well, they say it is for thermal reasons - 2 cards 25W each + 4 cards 15W each = 110W ; electrically it might have a wider margin.
Keep in mind that the 4 processors have a theoretical max of 520W so it adds up. But the fans at MAX were so strong (before I removed them) that I would have guessed they can easily dissipate 2000W. But what do I know.

I will wait and not plug anything until I have more info.

Meanwhile I found a 16x PCIe powered riser card for cheap and local (US shipping) so I will order one just to have it:

Powered PCI-E 16X to 16X Adapter Riser Extension Cable Molex Power Connector

What is happening tomorrow - is AMD releasing a driver update addressing the issue?

Those are some cool ribbon cables with power. I always worried that using ribbon cables would cause excessive voltage droop under load. This looks like it would take care of it. The only other issue would be noise with extending the length of the signaling which doesn't seem to impact much video cards for folks using these. I say that is the real solution no matter what card you get in that configuration or if one want to make a custom design giving flexibility to the video card location.

 

[petreza]

Thank you all for your advise.

...

ps
chaps, he wouldnt be purchasing this card to only run a desktop, that would be daft.
It will be put under load.

but op, if you really dont intend on utilising the power of this card, get something safer and cheaper.

Actually, for right now, I wanted something that will support the latest video standards - 4K 60Hz 4:4:4 color. I am sure there are cards (now) that will do this for $75-$125 but I didn't bother doing my homework. I also wanted something that will do decent 3D acceleration (not for gaming) with less watts. Eventually, when I need more 3D power I will sell this card at a loss and upgrade to a top of the line card.

Those are some cool ribbon cables with power. I always worried that using ribbon cables would cause excessive voltage droop under load. This looks like it would take care of it. The only other issue would be noise with extending the length of the signaling which doesn't seem to impact much video cards for folks using these. I say that is the real solution no matter what card you get in that configuration or if one want to make a custom design giving flexibility to the video card location.

Thanks! I was surprised at how easily and cheaply this issue COULD be solved. If the ribbon cable with separate power will actually solve the problem remains to be seen. For me extending the PCIe slot is a minor headache - the whole system is a custom setup so putting a bracket for a PCIe card is just one more thing to do. But if people with a regular system cases had to do this to use their new card, it would be unacceptable. From the little I read on the issue it seems the vast majority of the motherboards will not really have an issue with power draw unless they have also other stuff plugged in that draws a lot of power too.