Why no ALU hot-clock below two times base clock? S3 showed it with Chrome 400/500.
1.5 times base clock would a bit above previous ALU:TEX.
Considering the amount of shaders AMD uses, and the fact that heavy shader use is what's currently running into the powertune TDP limits, raising base clock of ALUs would just mean powertune kicks in more often.
That isn't necessarily bad if we look at an example below, but wouldn't be the most efficient use of resources.
I agree that it is more complex, but if you break it down to its bare elements then it is just an anti-Furmark switch.
Hardly, and it is definitely a lot more complex than previous power monitoring and throttling solutions on previous GPU solutions from both vendors.
Comparing onto GTX 580 right now as that's perhaps the worse possible type of power containment there is, app detection. If something like this is done you lower your clocks across the board thus everything is reduced in performance. Min, Avg, Max FPS would be affected.
Now with Powertune. What it allows AMD to do is allow for a higher base clock. without exceeding TDP requirements which are meant to prevent a card/chip from frying and destroying itself.
So, without Powertune, 6970 may have necessitated a lower base clock. Lets say Powertune when it kicks in reduces clocks to those levels. Now lets compare theoretical effects on games.
6970 w/PT but no throttling - higher clocks = higher min, higher average, higher max than 6970 without PT due to lower base clocks.
6970 w/PT but with throttling - same or lower clocks as 6970 without PT when throttling = higher min (same as above), higher average although not as high as above, variable max FPS could be higher, same, or lower than 6970 without PT.
In all cases, min FPS will be higher. Average FPS will be higher (unless during design they REALLY borked the chosen base clock speed). Max FPS may be higher, same, or lower.
Unless they boosted clocks so aggressively that the card is throttling the majority of the time, then you'll generally see an overall performance boost with powertune versus without powertune. Those exceptions generally being the outliers/power viruses/programs that stress only one singular part of a GPU in a pathological way. IE - generally not games.
In the very worse case scenario where the base clock was boosted so high that powertune was throttling 100% of the time you'd end up with a situation where min FPS = average FPS = max FPS which would likely be significantly faster than a non-powertune clocked GPU. But that wouldn't be a very efficient way to design a GPU. As well power consumption would be overall higher as now you're basically running the card at 100% power consumption 100% of the time (well, except when idle).
Of course, this is also going to depend on the granularity of throttling going on. If it's very course, then it may not be beneficial all the time ala Intels throttling in the past where clock speed would drop rather drastically rather than having a more gradual decrease to match increased load..
Powertune is by far the most exciting thing about Cayman, IMO with regards to increasing performance of video cards going forward as it'll allow for higher utilization of a card versus the same card with a base clock without powertune. This assuming it allows for a higher base clock as advertised.
The card itself may or may not be disappointing for a variety of reasons. But powertune is certainly something I'm looking foward to going forward.
Regards,
SB
