AMD: Speculation, Rumors, and Discussion (Archive)

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Taken from this link:
https://www.reddit.com/r/Amd/comments/4qmlep/rx_480_powergate_problem_has_a_solution/

The power usage etc. is defined in the PCI Express Card Electromechanical Specification. Please look at page 27 and 36 of the PCI Express® Base Specification Revision 3.0

From Page 27 "Document Organization"

"The PCI Express Base Specification contains the technical details of the architecture, protocol, Link Layer, Physical Layer, and software interface. The PCI Express Base Specification is applicable to all variants of PCI Express.
The PCI Express Card Electromechanical Specification focuses on information necessary to implementing an evolutionary strategy with the PCI desktop/server mechanicals as well as electricals. The mechanical chapters of the specification contain a definition of evolutionary PCI Express card edge connectors while the electrical chapters cover auxiliary signals, power delivery, and the adapter interconnect electrical budget."

Page 36 states the Reference Documents and the PCI Express Card Electromechanical Specification

And from the PCI Express™ Card Electromechanical Specification Rev. 1.1 (2.0 is behind a paywall, but wikipedia has the same information):

"A standard height x16 add-in card intended for server I/O applications must limit its power dissipation to 25 W. A standard height x16 add-in card intended for graphics applications must, at initial power-up, not exceed 25 W of power dissipation, until configured as a high power device, at which time it must not exceed 75 W of power dissipation. Refer to Chapter 6 of the PCI Express Base Specification, Revision 1.1 for information on the power configuration mechanism."
Click to expand...

As far as I know, and from what I can gather from leaked PCI-SIG papers, 81W is more or less the limit if you're abusing the tolerances as much as possible. AMD chose to do this because they're pushing the PCI-E and ATX specifications as far out of spec as is allowed to be able to slap a single 6-pin connector and use a cheaper board design and components.

I'm waiting on some replies from PCI-SIG and my AMD rep on this issue. I plan on writing up my findings asap, which might be tomorrow.
Click to expand...
 
They are just mentioning the PCI Express spec, there is also the ATX12V V2.x and also their Power Distribution configuration guidelines, along with Molex spec that I have also touched upon.
You can go above 75W even though it is not defined by PCI Express spec, but is by others.
It really breaks the debate into two parts; one around the PCI Sig certification-spec exceeded and the other around the actual power demand/distribution and impact.
Cheers
 
As long as GCN's generally decent power management knows it's blowing out its power budget, I suppose I can feel a little better.
My mistake seems to have been relying overmuch on the six-pin as some kind of ward against the usual TBP relationship with reality.
 
ninelven said:
Apparently, the voltage tolerances don't really matter because the overhead is in current (bad).

PcPer did a nice write up:
http://www.pcper.com/reviews/Graphics-Cards/Power-Consumption-Concerns-Radeon-RX-480
Click to expand...

Well at least pcper is doing testing with cheap mobos. It's what Toms should be doing.

"For our part, we are going to be plugging the Radeon RX 480 into a couple of older platforms and running it in some “bad case” scenarios…just to see what happens."
 
SimBy said:
Well at least pcper is doing testing with cheap mobos. It's what Toms should be doing.

"For our part, we are going to be plugging the Radeon RX 480 into a couple of older platforms and running it in some “bad case” scenarios…just to see what happens."
Click to expand...
Just checked some cheap PCIe slots. One can buy some slots really rated as low as 1.1A per pin. With five 12V pins in an PCIe slot, that equals exactly the 5.5A/66W with no reserves at all. With such slots I can imagine that there could indeed be problems, especially in the long run. At this point one can only hope that most mainboards use slots with slightly thicker contacts and a higher current rating.
 
Getting away of the "power gate" I'm actually happy to see the performance and see a mid range card performing like the last high end ones. Customs cards would be a very good choice.

Enviado desde mi HTC One mediante Tapatalk
 
BTW is there a possibility of having customs coolers that fit the reference pcb?

Enviado desde mi HTC One mediante Tapatalk
 
Esrever said:
When is the 470 and 460. It's so strange that release of the 480 has had no info for the other cards..
Click to expand...
Why is that strange? The 480 was announced separately from the 460 and 470. They will have a separate product availability and reviews timelines.
 
Don't see the problem with the card. I will be getting one for my gf this fall. It uses little power , performs better than the 390 and is only $230 for 8 gigs.

Best part is it replaces the ancient 6950 in her machine so the whole system should run cooler and put less strain on her power supply.
 
to me its very clear that AMD certified an internal sample running at lower clocks and/or with lower voltage. But due to pascal pressure, retail cards have been pushed above the sweet spot/certified sample. nothing uncommon in the industry...
 
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