10 Replies Latest reply on Jul 5, 2016 10:41 PM by brucer

    Does RX480 fail PCI-E specification?






      Flair changed to NEWS because this is now NEWS

      PC Perspective has confirmed most of what was said in this thread, thanks to all who helped





      UPDATE 22

      It has come to my attention that some people are erroneously interpreting the PCI-E specification document, claiming absurd things like the motherboard being determining the maximum power draw. Claiming that >300W is possible from the slot.

      The 300W figure is broken down as follows; 75W(slot) + 75W (6pin) + 150W (8pin)

      The reference to >300W configurations considers the following;

      8pin +8pin

      8pin + 8pin + 6pin

      It is patently untrue that you can draw more than ~75W within spec;


      Someone kindly sent me the link to the electromechanical specifications for PCI-E

      Page 44 onwards


      Information in this thread is interpreted incorrectly https://www.reddit.com/r/Amd/comments/4qmlep/rx_480_powergate_problem_has_a_solution/


      Update 23

      I believe this will be the last update.



      12V @ 5.5A WITH MAX 8% TOLERANCE

      3.3 @ 3.0A WITH MAX 9% TOLERANCE

      12V MAX = 71.3W

      3.3V MAX = 10.8W

      According to Tom's Hardware:

      RX480 GAMING (metro 4k) AVERAGE is 82W on 12V, 4W on 3.3V for a total of 86W


      Read these:



      The PCI Express® Base Specification Revision 3.0 is the wrong spec.

      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.

      Considering the maximum tolerances allowed (+8% voltage), taken from PCI-E electromechanical specifications, the RX480 is drawing, ON AVERAGE - NOT PEAK, 14% more power than the MAXIMUM from the 12v rail (82W vs 72W) and 5% more than the MAXIMUM in TOTAL (86W vs 82W).

      Update 24




      The PCI-SIG may not have to. My preliminary research indicates that licensees of a trademark, even non-exclusive licensees, have standing both to sue for trademark infringement and to request the ITC/CBP block the import of infringing (counterfeit) goods. See the answer to question 5 in this link. If that's true, NVidia can request that the US government block the import of all AMD products that violate the terms of the PCI Express licensing agreement.

      Disclaimer: I'm not a trademark attorney, so this could be incorrect. I am not providing legal advice to a client. No attorney-client relationship is created by this communication.

      Those peaks also violate the PCI Express spec, if they are not a measurement artifact. The card isn't allowed to change it's current draw faster than 0.1A per microsecond: that's the "maximum current slew rate" part of the spec image posted above. A 1A spike for 0.5 microsecond is 5A per microsecond: 50 times the max allowed current skew and seriously no bueno.

      Update 25; PCPer confirms!


      From PC Perspective:

      The easy fix to this whole ordeal is for AMD to have used an 8-pin power connector on the RX 480. The PCI Express spec allows an 8-pin connection to draw 150 watts on its own, leaving the power from the PCI Express connection on the motherboard for overhead. This is how NVIDIA designed the GTX 970 (two 6-pin connections) and how AMD designed the R9 380 (one 8-pin connection): both cards have 150+ watt TDPs with power supply overhead available to them. The new GeForce GTX 1070 has an identical TDP to the RX 480 (150 watts) but uses an 8-pin power connection to relieve any concerns at stock performance or while overclocking.

      I asked around our friends in the motherboard business for some feedback on this issue - is it something that users should be concerned about or are modern day motherboards built to handle this type of variance? One vendor told me directly that while spikes as high as 95 watts of power draw through the PCIE connection are tolerated without issue, sustained power draw at that kind of level would likely cause damage. The pins and connectors are the most likely failure points - he didn’t seem concerned about the traces on the board as they had enough copper in the power plane to withstand the current.

      AMD probably didn’t want to include a second 6-pin or upgrade to an 8-pin connection because of the impression it would give for a mainstream gaming card. Having two power connectors or an 8-pin might tell uninformed buyers that the RX 480 isn’t power efficient enough, that it might not work with an underpowered system and power supply, etc. My hope is that AMD’s partners paid attention to this data and are over building their power delivery to alleviate any concerns. We will know very soon.

        • Re: Does RX480 fail PCI-E specification?

          You are a true Prophet of Doom. You don't even own the card and here you are trolling...again.

            • Re: Does RX480 fail PCI-E specification?

              I dont, thats odd, then what is this for?


              amd bullshit.PNG


              When you dont know what your talking about you'll learn to keep your mouth shut 


              I guess you could call me that though, since I bought another new amd card, I must be wanting the punishment huh... 


              You'll learn real quick, I speak my mind and I dont lie...


              I'm literally afraid to put the rx480 in my old rig....

                • Re: Does RX480 fail PCI-E specification?

                  After your last "purchase" you advised everyone to stay away from AMD....now you say you bought another one and already spreading negativity and rumor-has-its. You are a piece of work.

                    • Re: Does RX480 fail PCI-E specification?

                      yep, I bought the 480 to replace my old r9-290.. going to sell the r9-290, and an old hd6850 and the Sapphire Fury and buy a 1070 or 1080..



                      I bought the 480 for the power efficiency to replace the 290 because that old computer stays on 24/7..



                      To add, I also recently stuck a 750watt seasonic gold rated psu in that old computer just for the efficiency, plus I needed a spare psu and the antec trupower 850 will work for a backup..

                      • Re: Does RX480 fail PCI-E specification?

                        if you read the links in what I posted you'll see the 480's were scoped "oscilloscope" and several verified it..  I'd like to hear more on it..

                        • Re: Does RX480 fail PCI-E specification?

                          This is a complete copy and paste from here..




                          doom off, this person on overclock.net knows his stuff

                          source: http://www.overclock.net/t/1604477/reddit-rx-480-fails-pci-e-specification/100#post_25305968

                          Originally posted by DaaQ on overclockers.net

                          "Ok, since the bandwagon is speeding along so fast that pitchforks are flying everywhere. I have wasted 45 minutes to read through this thread. I am going to provide some information I am pretty sure few will actually read. I will start by getting the stuff I am not going to bother providing any backup for first.

                          According to the internet, the PCIE slot pulling over 75w was from 2 reviewers out of 20, of the other reviewers who were shared this information, non were able to recreate the scenario. So not being able to recreate the current overdraw by other reviewers, really means something in itself. But AMD fail is AMD fail, such is the oh too familiar mantra. rolleyes.gif Anyone that comes at me with proof.gif or your argument is invalid. How about you actually do some reading if your so concerned with proof. I seen the above information earlier in the day and am not going to spend the time trying to convince people that won't be convinced anyway.

                          Now for the good stuff.

                          Here's a juicy bit from this link here, which ironically is where I heard some of the above. https://www.reddit.com/r/pcmasterrace/comments/4qfy9d/i_work_at_amd_the_time_has_come_to_ama_about/


                          Ektobuffer 3 points 3 hours ago "Maybe i can helb you out a bit Raja. I have just read the PCI-E 3 specifications and they are telling me something different. In my understanding the 75 watt isnt the maximum limit, its just the default value on startup of the motherboard. The motherboard it self sets the maximum allowed watt per slot in the "Slot Capabilities Register" which you can configure up to over 300 watt per slot. In the bits 7 to 14 "Slot Power Limit Value" you can set 250, 275, 300 and above 300 watt. This will be multiplied with bits 15 to 16 "Slot Power Limit Scale" in steps x1 ,x0.1, x0.01 and x0.001. So its up to the motherboard manufacturer and the power management on it how many watt the slot is capable of. The Specifications do define the protocol and not the hardware specs of the PCI-E slot. If a manufacturer uses better parts which can handle higher amps on the contacts and the lines, they can allow the devie in the slot a higher power consumption than 75 watt via these registers. Sadly most people doesnt even read the specifications and judge things they dont understand." http://composter.com.ua/documents/PCI_Express_Base_Specification_Revision_3.0.pdf

                          Now the link provided in that quote is really interesting. ( DL it Looniam if you don't have it you will love it ) Hopefully those that are so inclined actually spend some of their time and actually read some of the info in that link.

                          So it's late and I need to get to bed, but this is what I quickly found in that 800+ page document.

                          Quote: "Power limits on the platform are typically controlled by the software (for example, platform firmware) that comprehends the specifics of the platform such as: 15 Partitioning of the platform, including slots for I/O expansion using adapters Power delivery capabilities Thermal capabilities This software is responsible for correctly programming the Slot Power Limit Value and Scale fields of the Slot Capabilities registers of the Downstream Ports connected to slots. After the value has 20 been written into the register within the Downstream Port, it is conveyed to the adapter using the Set_Slot_Power_Limit Message (see Section The recipient of the Message must use the value in the Message data payload to limit usage of the power for the entire adapter, unless the adapter will never exceed the lowest value specified in the corresponding form factor specification. It is required that device driver software associated with the adapter be able (by reading the values of 25 the Captured Slot Power Limit Value and Scale fields of the Device Capabilities register) to configure hardware of the adapter to guarantee that the adapter will not exceed the imposed limit. In the case where the platform imposes a limit that is below the minimum needed for adequate operation, the device driver will be able to communicate this discrepancy to higher level configuration software. Configuration software is required to set the Slot Power Limit to one of the 30 maximum values specified for the corresponding form factor based on the capability of the platform. The following rules cover the Slot Power Limit control mechanism: For Adapters: Until and unless a Set_Slot_Power_Limit Message is received indicating a Slot Power Limit 35 value greater than the lowest value specified in the form factor specification for the adapter's form factor, the adapter must not consume more than the lowest value specified. PCI EXPRESS BASE SPECIFICATION, REV. 3.0 528 An adapter must never consume more power than what was specified in the most recently received Set_Slot_Power_Limit Message or the minimum value specified in the corresponding form factor specification, whichever is higher."

                          Page 527 to be specific, this concerns slot power limit control. The above sounds to me either, vBIOS or BIOS level. Would be quite interesting if the motherboard was responsible for assigning the slot power limit wouldn't it?

                          devil.gif away."

                          Folks, we have a solution, bios update is probably all that's needed and the rx 480 is good to go. powergate goes back into the ground just as it was getting started.

                          • Re: Does RX480 fail PCI-E specification?

                            Evidently its true...


                            It looks like a bios update is going to be needed from the sounds of it.. and its stuff like this that makes me weary of amd nowadays, this amd isnt the amd of old...


                            this will also lessen the voltage to the gpu, and decrease performance if I understand correctly.


                            I'm actually afraid to put a new component in my pc, guess there's a first for everything, huh..

                            • Re: Does RX480 fail PCI-E specification?

                              Figured I'd let you be the first to know




                          • Re: Does RX480 fail PCI-E specification?

                            just trolling again, guess I was just asking another valid question huh?


                            Official Statement from AMD on the PCI-Express Overcurrent Issue | techPowerUp