PC Graphics

[EFermi]

What is maximum safe Power Limit to set for 6900XT?! 

I have a reference design board from ASUS, and I raised it's power limit via MorePowerTool to the base of 310W, then later lowered it slightly to 292W base (I specify "base" because there's still a +15% overclock raise to that, which gives a total of 357W and 336W maximum peak consumption respectively). 

My concern is that the PL provided in MPT (and monitored by apps like RTSS) is only for the GPU die itself, while there still are elements on the PCB, specifically memory, that require some power to run.

In reference design cards, there are 2x8-pin connectors, which result in sum of 300W power, and PCI-E lane which supplies up to 75W, for a grand total absolute max of 375W. The highest base draw in factory-OC'd 6900XT GPUs from different vendors that have 2x8-pin is 281W (Nitro+, Red Devil, etc.), which implies this is safe to use. But what about higher values? If we give the GPU die a max of, say, 357W (310 base + 15% overclock), it only leaves barely 20W of power for the PCB components if calculated within limits, and everything above is power lines overload, which is not much IF it's only, like, extra 10W over the designed maximum, but it may be higher, who knows, I don't have fancy watt-meters to measure the power draw, only software monitoring. Hence my decision to lower the base power limit to 292W to be on the safe side.

But the question still stands: what is the maximum safe power limit for a 6900XT? I kinda sorta want to go back to 310W base / 357W max, but I also don't want to overload my power lines excessively, so what is your advice on that? 

[goodplay]

If you don't plan on overclocking, then Gold or higher psu 850-900W is sufficient (depending on card/make/model).

[EFermi]

Errm... That's not what I'm asking, lol. I have Seasonic Prime TX-1000, but my question is not about PSU unit, it's about how much wattage is safe to apply for a GPU that is only connected via 2x8-pin.

[goodplay]

Then you be looking to find overclockers forum posts, OCUK (6900xt owners thread, page 12 is a good start ?) has one with setup suggestions.

And of course 2 separate 8 pin cables. 

[Thanny · Accepted solution]

The official recommended limits for the 8-pin PCIe graphics cable is 150W, but it will carry quite a bit more.  A quality power supply will often be able to supply 300W+ on each 8-pin connector.

Suffice it to say, nothing you change about the power limit in software is going to be a problem, unless you have a very shoddy PSU.

[EFermi]

Thanks. I finalized my config with setting base PL to 300 watts + 11% overclock through Afterburner, which resulted in max TDP of 333W, sometimes barely peaking up to 335-336 according to CPU-Z monitoring. It's roughly 33~35 watts above fully overclocked default setting (which is, if anybody wonders, 255W base, with an obvious maximum of +15% overclock - around 300 watts, give or take a few), and 10~15 watts above such factory OC'd models as Sapphire Nitro+, ASRock Phantom Gaming D or PowerColor Red Devil (which all have a 281W base, with standart +15% OC results in roughly 323~325W). One interesting point is that, even though some custom PCB cards have 3x8-pin power connectors (ASRock PGD or recently announced MSI Trio, for example) they still only feature a 281W base power limit. What is the reason for triple 8 pins then? Why would I pay extra $150 for these when it's no difference? For fancy-looking cooling that, according to techpowerup tables, gets you a whopping 2°C cooler card? For comparison, quite a few 3x8-pin 3080s (ASUS Strix in all versions, EVGA FTW3 and FTW 3 Ultra, MSI Suprim, Palit GameRock OC and a couple more models) have a maximum power limit of 430-450W. Four hundred and thirty to four hundred and fifty watts! This is what you do with 3x8-pin! (Also, MSI Trio 3080/3090 can f@©k right off - same stuff as with 6900 series - powerlimit is barely raised by a dozen watt above reference despite packing three 8 pins).

[Thanny]

Power consumption goes up very non-linearly with clock speed.  Having triple 8-pin connectors lets people who enjoy spending a lot of time searching for the limits of overclocking do so without worrying about input power.

For a normal person who does a modest overclock at most, it's pointless.  That doesn't mean the extra cost is completely unjustified, because the card with more power inputs might also have a better binned chip, which will run at higher clock rates with lower voltages.