Friday, July 8th 2016

AMD Releases PCI-Express Power Draw Fix, We Tested, Confirmed, Works

Earlier today, AMD has posted a new Radeon Crimson Edition Beta, 16.7.1, which actually includes two fixes for the reported PCI-Express overcurrent issue that kept Internet people busy the last days.

The driver changelog mentions the following: "Radeon RX 480's power distribution has been improved for AMD reference boards, lowering the current drawn from the PCIe bus", and there's also a second item "A new "compatibility mode" UI toggle has been made available in the Global Settings menu of Radeon Settings. This option is designed to reduce total power with minimal performance impact if end users experience any further issues."

In order to adjust the power distribution between PCI-Express slot power and power drawn from the PCI-Express 6-pin power connector, AMD uses a feature of the IR3567 voltage controller that's used on all reference design cards.
This feature lets you adjust the power phase balance by changing the controller's configuration via I2C (a method to talk to the voltage controller directly, something that GPU-Z uses too, to monitor VRM temperature, for example). By default, power draw is split 50/50 between slot and 6-pin, this can be adjusted per-phase, by a value between 0 to 15. AMD has chosen a setting of 13 for phases 1, 2 and 3, which effectively shifts some power draw from the slot away onto the 6-pin connector, I'm unsure why they did not pick a setting of 15 (which I've tested to shift even more power).

The second adjustment is an option inside Radeon Settings, called "Compatibility Mode", kinda vague, and the tooltip doesn't reveal anything else either. Out of the box, the setting defaults to off and should only be employed by people who still run into trouble, even with the adjusted power distribution from the first change, which is always on and has no performance impact. When Compatibility Mode is enabled, it will slightly limit the performance of the GPU, which results in reduced overall power draw.

We tested these options, below you will find our results using Metro Last Light (with the card being warmed up before the test run). First we measured power consumption using the previous 16.6.2 driver, then we installed 16.7.1 (while keeping Compatibility Mode off), then we turned Compatibility Mode on.

As you can see, just the power-shift alone, while working, is not completely sufficient to reduce slot power below 75 W, we measured 76 W. As the name suggests, the changed power distribution results in increased power draw from 6-pin, which can easily handle slightly higher power draw though.
With the Compatibility Mode option enabled, power from the slot goes down to 71 W only, which is perfectly safe, but will cost performance.

AMD has also promised improved overall performance with 16.7.1, so we took a look at performance, using Metro again.
Here you can see that the new driver adds about 2.3% performance, which is a pretty decent improvement. Once you enable Compatibility Mode though, performance goes down slightly below the original result (0.8% lower), which means Compatibility Mode costs you around 3%, in case you really want to use it. I do not recommend using Compatibility Mode, personally I don't think anyone with a somewhat modern computer would have run into any issues due to the increased power draw in the first place, neither did AMD. It is good to see that AMD still chose to address the problem, and solved it fully, in a good way, and quick.
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147 Comments on AMD Releases PCI-Express Power Draw Fix, We Tested, Confirmed, Works

#26
xkm1948
RejZoR said:
That would make more sense, 40A*1.5V is 60W. If that's a 125°C rating, at lower temperatures we can still be talking around 80-100W. That's still huge.

@Shamalamadingdong
Yeah, I'm aware of the risks, but that applies to every overclock. Still, the headroom can be a lot higher than around 150W as initially thought. If user has PSU powerful enough to feed 6pin, VRM is there to deliver it if needed. Far beyond the original specs. Meaning AIB's only have to slam better cooling on reference design. They don't even have to redesign PCB and components on it to gain headroom.
Gusteberg over OCN is working on editing RX480 BIOS for increased power limit. With all power limit removed and heat factor dealt with the card should run 1.4GHz to 1.5GHz easily.
Posted on Reply
#27
$ReaPeR$
xkm1948 said:
I am having stability issue with this new driver on FuryX. 1100 OC is no longer stable no matter what amount of vcore offset is applied now. Played CSGO for 30mins and it crashed on me which have not happened since launch driver. Lower down to 1075OC and it still would crash. It can't even pass the 3DMark FireStrike Stress test now. I use DDU between all of my driver installations so it is definitely not the problem of driver files conflict. Reverted back 16.6.1 and everything is back to normal. Passed 100 loops of FSE Stress test at 99.5% for 1100 OC.

Very likely RTG is focusing on 480 driver now and somehow messed up driver support for previous gen cards. Guess I will just wait until a newer driver that does not solely focus on RX480 then.

And yes I have already submitted the problem to RTG.
damn! with their budget though i dont think they can "multitask" that much..
Posted on Reply
#28
xkm1948
$ReaPeR$ said:
damn! with their budget though i dont think they can "multitask" that much..
Good thing is there are nothing new I needed from 16.7.1 at this moment. I thought FuryX would get the Wattman but nope. Oh well, I can work with traiditional way of OC. :D
Posted on Reply
#29
GhostRyder
xkm1948 said:
I am having stability issue with this new driver on FuryX. 1100 OC is no longer stable no matter what amount of vcore offset is applied now. Played CSGO for 30mins and it crashed on me which have not happened since launch driver. Lower down to 1075OC and it still would crash. It can't even pass the 3DMark FireStrike Stress test now. I use DDU between all of my driver installations so it is definitely not the problem of driver files conflict. Reverted back 16.6.1 and everything is back to normal. Passed 100 loops of FSE Stress test at 99.5% for 1100 OC.

Very likely RTG is focusing on 480 driver now and somehow messed up driver support for previous gen cards. Guess I will just wait until a newer driver that does not solely focus on RX480 then.

And yes I have already submitted the problem to RTG.
That's unfortunate, it didn't effect my 290X's and their overclocking. I tested it with some BF4 last night and no problems with same settings though I don't see anything that I gained either so probably could have not downloaded it.
Posted on Reply
#30
$ReaPeR$
xkm1948 said:
Good thing is there are nothing new I needed from 16.7.1 at this moment. I thought FuryX would get the Wattman but nope. Oh well, I can work with traiditional way of OC. :D
cool, you look like you know your stuff anyway.. :)
Posted on Reply
#31
cdawall
where the hell are my stars
laszlo said:
mb don't have built in a current limiter and any consumer attached to it can draw more till something is kaboom
Depends on board I have more than one high end board that allowed per slot wattage limits. Most of which I could go as high as 150w...
Posted on Reply
#32
HD64G
ZoneDymo said:
well thats very neat.
So it actually works and the performance does not suffer :)

Nice job AMD.

@tPU and chance of running a few more games to see how they react?
Almost sure that for the next GPU review (custom RX480 probably) W1z will test them with Crimson 14.7.1 as he always does :)
Posted on Reply
#33
laszlo
RejZoR said:
So, all phases can churn out 240W theoretical load and realistic max being 120W on 6pin phases and 75W on PCIe phases. That's still 195W which ain't that bad, giving some headroom. If you can cool it well enough.
you understood wrong.... 6 pin isn't max out with 120w...can deliver min. 150w....if psu rail have juice...
Posted on Reply
#34
RejZoR
I know that, I was talking based on what phases can actually deliver. If 3 phases are dedicated to 6pin and each is 40W, then that's 120W. But someone later clarified it's 40A and not 40W...
Posted on Reply
#35
Agiels
so is a driver or what ?? i was having big peaks of current in my r9 280, maybe it got fixed for me too ?
Posted on Reply
#36
RejZoR
Agiels said:
so is a driver or what ?? i was having big peaks of current in my r9 280, maybe it got fixed for me too ?
Very unlikely since this is RX480 specific control of it's VRM segment. I very much doubt they'd somehow change old R9 280 as well with it.
Posted on Reply
#37
Agiels
damn it, i think my PSU its failing to hold my system, i will get a EVGA Supernova 750W or a CX750M ...
Posted on Reply
#38
RejZoR
$ReaPeR$ said:
damn! with their budget though i dont think they can "multitask" that much..
Still, Fury X is still their current flagship. It deserves same attention as new RX generation. @xkm1948 send a bug report to AMD.
Posted on Reply
#39
xkm1948
RejZoR said:
Still, Fury X is still their current flagship. It deserves same attention as new RX generation. @xkm1948 send a bug report to AMD.
Read my thread dude, already sent. Thanks for the tag though. :D

I don't buy cards for showing epen. I use them for work and entertainment. So far my FuryX has been more than awesome for VR as well as OpenCL computing.

Going back to Nekopalive now.
Posted on Reply
#40
Agiels
cant be more agree with you, for me no company is better than the other, i focus on costs and perfomance, no of those companys will give you a damn product for free, they will preffer to have ur blood first !

for what i see, nVidia is always more spensive than AMD at the same level of performance, atleast here in Cuba it this, for example, GTX960 here cost around 250/270$ at that same price tag and more performance i will neve buy that above an r9 280x (220$) or a r9 380x (270$)
Posted on Reply
#41
buildzoid
Turns out I messed up the current rating at 125C. The RX 480 Vcore VRM is 6 phases composed of a MDU1514 high side FET and an MDU1511 low side FET. The MDU 1514 has a continuous drain current of 66A @ 25C case temperature and just under 30A at 125C. It has a pulsed current rating of 100A however the pulse duration or frequency isn't specified so it's not all that useful . The low side MDU1511 has a continuous drain current of 100A at 25C case temperature and goes down to about 66A at 125C. So the low side of the VRM can handle 396A of current at 125C and the high side should be able to keep up with that depending on the duty cycle. A 100% safe rating for the high side is 180A @125C at any core voltage setting. Realisticly the VRM shouldn't get anywhere near that hot and you will have a lot more current to play with on both the high and low sides.
Posted on Reply
#42
$ReaPeR$
entropic said:
they really should focus on the boot issue with high refresh rate using dvi, multi high refresh monitors increased power draw and displayport incompatibility with htc vive, but i guess any amd fault to bash is better than admitting nvidia has any
i didnt know about these problems, could you care to post some links please?
Posted on Reply
#43
cdawall
where the hell are my stars
I don't understand why people care so much about brand if it works it works if it doesn't it doesn't. Both companies have released junk for whatever reason. Move on.

$ReaPeR$ said:
i didnt know about these problems, could you care to post some links please?
Can you use google?

https://www.techpowerup.com/223669/geforce-gtx-pascal-faces-high-dvi-pixel-clock-booting-problems

http://www.tomshardware.com/news/nvidia-vive-displayport-incompatible,32204.html
Posted on Reply
#44
Frick
Fishfaced Nincompoop
There's a word for people stamping degrading titels on others without knowing the person in question: People stampting degrading titles to others sans knowing the persons they apply the stampt upon. And it's always ugly, on so many levels.
Posted on Reply
#45
cadaveca
My name is Dave
Since this option was a function of the VRM controller, I was really surprised AMD didn't do this from the start, especially considering that it barely affects performance.

Nice to see compatibility mode for those users with older(within limits) PSU/mobo combos can safely add in multiple 480s, too.

However, If I was AMD, I would have had these things ready at the launch and advertised them as features to boost up the bullet points and bring in more consumer confidence. Hopefully future releases will take this situation as a consideration and they'll put it to good use. Sad to see hardware released that doesn't take advantage of all it has to offer; excellent to see it used properly so quickly.
Posted on Reply
#46
$ReaPeR$
cadaveca said:
Since this option was a function of the VRM controller, I was really surprised AMD didn't do this from the start, especially considering that it barely affects performance.

Nice to see compatibility mode for those users with older(within limits) PSU/mobo combos can safely add in multiple 480s, too.

However, If I was AMD, I would have had these things ready at the launch and advertised them as features to boost up the bullet points and bring in more consumer confidence. Hopefully future releases will take this situation as a consideration and they'll put it to good use. Sad to see hardware released that doesn't take advantage of all it has to offer; excellent to see it used properly so quickly.
that was their stupidity.. the whole problem could be avoided so easily.. i really cant get amd sometimes..
Posted on Reply
#47
W1zzard
cadaveca said:
Since this option was a function of the VRM controller, I was really surprised AMD didn't do this from the start, especially considering that it barely affects performance.

Nice to see compatibility mode for those users with older(within limits) PSU/mobo combos can safely add in multiple 480s, too.

However, If I was AMD, I would have had these things ready at the launch and advertised them as features to boost up the bullet points and bring in more consumer confidence. Hopefully future releases will take this situation as a consideration and they'll put it to good use. Sad to see hardware released that doesn't take advantage of all it has to offer; excellent to see it used properly so quickly.
They could have just connected one more phase to the 6-pin, instead of 50/50, very easy to do during board design stage.
Posted on Reply
#48
cadaveca
My name is Dave
W1zzard said:
They could have just connected one more phase to the 6-pin, instead of 50/50, very easy to do during board design stage.
But that might have given the potential for higher clocking and cannibalized a future SKU. :P
Posted on Reply
#49
AsRock
TPU addict
Thanks W1zzard for putting the time and effort in to this.
Posted on Reply
#50
the54thvoid
cadaveca said:
But that might have given the potential for higher clocking and cannibalized a future SKU. :p
Is the rumour not that the higher SKU, RX490 is a dual card?
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