R9 290X Variance

[ICDP]

Without beating about the bush, IMHO AMD tried to have their cake and eat it. There is no question that the reference R9 290/X cooler is not good enough to keep the GPU cool and quiet at the same time. What we the consumer ended up with is an excellent GPU with a poor cooler. We can choose between two modes.

Quiet mode: Acceptable noise level with some very bad throttling. This also seems to be the mode where the most variance will crop up.

Or

Uber mode: Little to no throttling but at the expense of a very loud fan profile.

We can't have both at the same time with the current reference cooler. There is essentially nothing wrong with how R9 290/X boost/clock control works apart from the reference cooler. I think the reference cooler is just not up to the job and once even semi decent custom cooled versions are released there will be no need for a quiet mode.

 

[ViRGE]

re.
The GPU does not have a minimum core clock.

That's a really good post ICDP, but I would like to make one correction. Hawaii in fact does have a minimum core clock, and I think everyone here would recognize it as such.

Assuming we're already at 95C and 40% on a 290X, then there are two scenarios that can play out while the card backs down from its maximum boost clock. If the card can maintain equilibrium above 727MHz - this being the minimum clockspeed as ID'd by AT, Tom's, etc - then it stays in its boost state, modulating clockspeeds while letting the GPU hold at 95C and 40% fan speed.

However if the card drops to 727MHz, then it changes its behavior. At this point the card will not let the clockspeed drop further, and instead it will raise the fan speed above 40% to maintain equilibrium. Or to use AT's formulas:

Boost Throttle Priority: Power = Fan Speed + Temperature

Base Throttle Priority: Power = Temperature > Fan Speed

From a temperature/cooling perspective, 727MHz is the absolute minimum. There isn't any practical scenario where a properly constructed 290X would be unable to cool itself at a higher fan speed (100% would be 6000 RPM or so). Given that setup, clockspeeds simply can't be any lower than this, making it our minimum.

Now there is the matter of power consumption, and I think that's what's leading some people to think that there's no minimum clockspeed. The 290X cannot violate its power settings, so it will drop clockspeeds and voltages to whatever state is required to stay under the limit. I haven't seen this documented on 290X, but from what I understand if it were to happen the card would drop to its "low-3D" state that's typically reserved for Blu-Ray playback and other intermediate loads. The important part being that it's no longer at its full-3D/base state, but rather is in a special state altogether that cannot be achieved (under full load) by any regular workload.

I bring that up because unlike the power/temp throttling mentioned above, the power throttling is unchanged from how it behaves on the 7970 or even the 6970. Both of those cards will drop to a lower state if they exceed their power limits, this being the primary purpose of the original version of PowerTune. But at the same time I don't think anyone would say that the 7970 or 6970 have a variable clockspeed, or even that their base clockspeeds aren't their real clockspeeds. For all intents and purposes those are 925MHz and 880MHz cards respectively.

So why would the minimum clockspeed on 290X be defined any differently? The 290X is a card with a minimum/base clockspeed of 727MHz, and a boost clock of 1000MHz. It simply boosts virtually the entire time, which is why we don't see 727MHz. But 727MHz is a very real floor, as the card will let its clockspeeds drop to that level before taking more aggressive action to hold the line.

 

[Silverforce11]

Yup. The R290 floor is 662mhz, if it still cannot maintain that clock with up to 47% fan speed, it will override and spin the fans faster to mantain it.

Whats weird is if it senses high ambient, it will auto override that 47% cap and therefore spin faster while ALSO trying to boost as high as possible. Its weird because it reaches around 75% fanspeed in my closed case while boosting above 880mhz mining. If I open the case, it caps fanspeed to 47% but downclocks to 662 mhz..

Edit: I say its weird, because its counter-intuitive, in a hotter ambient, the card should downclock more to assist in lower temps/fan speed.

 

[ICDP]

Thanks for the corrections ViRGE and Silverforce11. I will update my post to reflect the accurate facts.