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[Reddit] RX 480 fails PCI-E specification - Page 77  

post #761 of 1129
Quote:
Originally Posted by The Stilt View Post

And where is the measurement how much power is drawn from the PCI-E slot itself?
And is MSI 390X Gaming a Hawaii based reference design? rolleyessmileyanim.gif

Practically the AIBs can deviate from the reference design as much as they wish with their custom cards. And in many cases they do, either to lower the BOM or to improve the overclocking headroom.
Some pages state that the three wired 12v on 6+2cables can handle 150w so why AMD didnt use 6+2 instead 6?
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post #762 of 1129
Quote:
Originally Posted by PontiacGTX View Post

Some pages state that the three wired 12v on 6+2cables can handle 150w so why AMD didnt use 6+2 instead 6?

Wanted to do this against miners. Blow their MBs.
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post #763 of 1129
Quote:
Originally Posted by ZealotKi11er View Post

Wanted to do this against miners. Blow their MBs.
or maybe they were trying to keep 480 under low production costs but they would get sued due to damages which doesnt seem like a good idea if they want to get good PR or gain marketshare
Edited by PontiacGTX - 7/3/16 at 12:00pm
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post #764 of 1129
Quote:
Originally Posted by PontiacGTX View Post

Some pages state that the three wired 12v on 6+2cables can handle 150w so why AMD didnt use 6+2 instead 6?
Maybe the pcb was designed for HBM in mind and since hbm use low power that kind of pcb desing could work.
post #765 of 1129
Quote:
Originally Posted by Bauxno View Post

Maybe the pcb was designed for HBM in mind and since hbm use low power that kind of pcb desing could work.

No..

Most oems use psus with 6 pin only. Thats the only reason i believe.
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post #766 of 1129
Quote:
Originally Posted by Alastair View Post

Why is the testing being done at +50% power limit.

Maybe to show that the slot can provide the power? that the connector is not going to melt, or spontaneously combust. IDK due to the language barrier and didn't rewatch the beginning with the captions on. Just an assumption on my part.
post #767 of 1129
Quote:
Originally Posted by Dargonplay View Post


"The real issue"

rolleyes.gif

I'm happy you have that so strictly defined. For me I'd rather have a slightly higher PCIe X16 average power consumption of 79W with lower DC cycle peaks like with the RX 480 than a lower average power consumption of 73W but 45 monstrous 225W+ peaks over the PCIe X16 MOBO slot every 60 seconds like with the GTX 960.

But that's just me I guess.

 

I'd rather have neither. Looks like you need to look up what Joule's First Law (or Joule-Lenz Law) is. It is extraordinarily applicable to why constantly high amperage through a conductor is really bad (hint, it is proportional to the square of the current). Constant spiking is bad for another reason: thermo-mechanical fatigue. However, constant high amperage is more likely to show damage sooner than thermal fatigue. Unless you can somehow cool those conductors properly, there is actually very real physical damage possible due to the conductor becoming far too hot.

post #768 of 1129
Here is an interesting bit from PCIE CEM 1.1
Quote:
IMPLEMENTATION NOTE
Software Update of the Slot Power Limit
System firmware must update the slot power limit to the system's allocated value for the PCI
20 Express add-in card (e.g., graphics) and ensure the completion of this update prior to invoking the
option ROM for that add-in card's PCI Express function. If the initial slot power limit value is set
by hardware initialization, then any attempt by software to change that value must be verified by that
software prior to initializing the add-in card. Subsequent updates by the system firmware or
operating system software, if any, may only increase the slot power limit value. However, after a
25 card is reset, the initial slot power limit value may be lower than the previous value. The maximum
power level for an add-in card must be assigned by the system firmware during PCI Express
configuration. For graphics, the power level assigned will be dependent on the platform’s support
of the PCI Express x16 Graphics 150W-ATX Specification, Revision 1.0 (including the supplemental
power cable)

And here is from PCIE base specification rev 3
Quote:
6.8. Power Budgeting Capability
With the addition of a hot-plug capability for adapters, the need arises for the system to be capable
of properly allocating power to any new devices added to the system. This capability is a separate
and distinct function from power management and a basic level of support is required to ensure
proper operation of the system. The power budgeting concept puts in place the building blocks that
5 allow devices to interact with systems to achieve these goals. There are many ways in which the
system can implement the actual power budgeting capabilities, and as such, they are beyond the
scope of this specification.
Implementation of the Power Budgeting Capability is optional for devices that are implemented
either in a form factor which does not require hot-plug support, or that are integrated on the system
10 board. Form factor specifications may require support for power budgeting. The devices and/or
adapters are required to remain under the configuration power limit specified in the corresponding
electromechanical specification until they have been configured and enabled by the system. The
system should guarantee that power has been properly budgeted prior to enabling an adapter.
6.8.1. System Power Budgeting Process
Recommendations
It is recommended that system firmware provide the power budget management agent the following
15 information:
Total system power budget (power supply information).
Total power allocated by system firmware (system board devices).
Total number of slots and the types of slots.
System firmware is responsible for allocating power for all devices on the system board that do not
20 have power budgeting capabilities. The firmware may or may not include devices that are connected
to the standard power rails. When the firmware allocates the power for a device that implements the
Power Budgeting Capability it must set the System Allocated bit to 1b in the Power Budget
Capability register to indicate that it has been properly allocated. The power budget manager is
responsible for allocating all PCI Express devices including system board devices that have the
25 Power Budgeting Capability and have the System Allocated bit Clear. The power budget manager is
responsible for determining if hot-plugged devices can be budgeted and enabled in the system.
There are alternate methods which may provide the same functionality, and it is not required that
the power budgeting process be implemented in this manner.

All I got time for right now. Again it appears to be software related, not "pcb designed wrong"
post #769 of 1129
Quote:
Originally Posted by looniam View Post

NO it does not!

if you have a 150 watt card then it would have to use BOTH (spec'd) 75 watt sources. and it IS a pci-sig requirement to keep those sources (connector/slot) separate; why the two vrm banks aren't tied together.

If your graphics card need around 150W, you would normally either use a 2x6pin or 1x8pin Power. With this configuration, your hardware could never exceed the 75W limit of the the PCI-SLOT. The extra power connector usually supply the GPU-core, while the PCI-Express bus handles the rest like the built on RAM and coolers.

Since RX480 chip is rated for 110W TDP, this would be best solved with one 8pin + PCIE-SLOT. There would be even room for overclocking, because the 150W of the 8pin can be violated without problems, as the 295x2 shows already.

Quote:
Originally Posted by PontiacGTX View Post

Some pages state that the three wired 12v on 6+2cables can handle 150w so why AMD didnt use 6+2 instead 6?

The standard 6pin can handle up to 150W easily. Only limit is how much the pins can handle. It can go until the caps and the plastic around it starts to burn because of the heat. At this point it can only be speculated why AMD didn't handle this better from the very beginning.

Quote:
Originally Posted by PontiacGTX View Post

or maybe they were trying to keep 480 under low production costs but they would get sued due to damages which doesnt seem like a good idea if they want to get good PR or gain marketshare

In my opinon the lower production costs were not the reason. I speculate the RX480 was a last-minute-job. The clocks, temperatures and power consumption probably looked good in the engineering samples, but the final production pieces did suddenly exceed those values by a large scale. To not get bad PR as you say, it is possible AMD just went with it. Had they brought the famous Polaris with double-6-pin or 8-pin, the fans would not be happy. The power saving promises could not hold their ground. Yet to fix this it would have taken AMD several months. Since AMD was already behind in release schedule in comparison to Nvidia, further delasy were not allowed to happen at all.

Taken the rumors of heat / clocking issues of Polaris(?) coming from Ojou10 here in the forum and Kyle Bennet from HardOCP, there could be some truth behind it. Both were ripped teribbly by the fanboy-crowd. As it seems, they were right to a certain extend.
Edited by Hardware Hoshi - 7/3/16 at 1:24pm
post #770 of 1129
Check this out. According to GPU-Z his GPU rusn at 1.05V (instead 1.15V or higher) and it use around 105W (max)?! What is happening?! AMD went for quantity?

Or maybe wrong profiles?!
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