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.
Anyone that comes at me with
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.
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
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 126.96.36.199). 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
The following rules cover the Slot Power Limit control mechanism:
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
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?