Joel (joel.hruska.delete@this.gmail.com) on April 29, 2015 3:12 pm wrote:
> Klimax (danklima.delete@this.gmail.com) on April 29, 2015 12:58 pm wrote:
> > Joel (joel.hruska.delete@this.gmail.com) on April 29, 2015 12:26 pm wrote:
> > > David Hess (davidwhess.delete@this.gmail.com) on April 29, 2015 8:38 am wrote:
> > > > Pierre (Boutoukoat.delete@this.yahoo.fr) on April 29, 2015 4:38 am wrote:
> > > > >
> > > > > Dissipated power is O(frequency) and O(squared voltage). The article mention the voltage could be reduced
> > > > > by 200 millivolts, e.g. go from 0.9 to 0.7 volts. This mean a reduction of power of 40%, and in layman
> > > > > terms, 40% more battery life on a processor 4 times cheaper. Reasoning at constant power and ignoring
> > > > > o a lot of details, frequency could increase by 40% if voltage goes from 0.9V to 0.7V. However, most of
> > > > > the perceived performance out of a processor comes from memory speed (unchanged ...) , parallelism and
> > > > > integration of co-processors like GPU and NICs (more transistors), and software benchmarks.
> > > >
> > > > Power density is also becoming a limiting factor. Heat pipes helped here however they have their own
> > > > hard power density limits and now require heat spreaders between the CPU and evaporator. If you reduce
> > > > the power by 40% but have the same number of transistors in 1/4 of the area, then the power density
> > > > increases by 160%. Raising the frequency by 40% and keeping the power constant would increase the power
> > > > density by 300%. Either the junction to case thermal resistance has to be lowered (diamond?) or a higher
> > > > junction temperature is needed which will adversely affect reliability and leakage.
> > > >
> > > > > For the last 10 years, frequency of desktops for gamers has not increased (peak around 4 Ghz on
> > > > > the most expensive Intel CPUs). It looks unlikely to change in the near future, and the trend
> > > > > to add more cores will continue. I hope this helps to answer your obsolete question "how faster
> > > > > ?" typical from the 90's. Right questions now are "how cheaper ?" , "how longer ?" ...
> > > >
> > > > AMDs current CPUs top out in the 4 GHz range as well. Adding more cores to take advantage of higher
> > > > density processes is going to run up against power density limits and most applications including
> > > > games cannot take advantage of more cores anyway. Do any games make use of more than 2 cores?
> > > >
> > >
> > > Yes. There are many modern titles that can make some use of up to four cores, though
> > > not much scales past that. DX12 is expected to vastly improve this scenario; it
> > > allows for effective multi-threading in ways that DX11 never supported.
> > >
> > > Early DX12 games and applications can take full advantage of all eight
> > > cores on a Haswell-E system and see performance gains from doing so.
> >
> > There won't be likely any real jump. Those early examples tend to be badly written benchmarks
> > at best intended to present severely contrived case, which in practice won't exist.
> > (Not to mention that current engines don't make use of half of DX11 anyway) Also DX12
> > and co makes very bad trade offs regarding future changes in GPUs. (IMO)
>
>
> Yeah, every developer I've spoken to -- and I've spoken to more than a few -- disagrees with that.

And I have analyzed quite few cases. And I say, that developers tend to be at best average in using available options and terminally overestimating things they think they need. (Their general solution is wrong answer to wrong question)

There are still to this day rare instances of correct use of DCL. (Driver Command Lists) They frankly have no standing.

> Mantle provides real evidence as well. Average performance uptick for AMD APUs using Mantle is about
> 13% with another 13% improvement in performance per watt. DX12 allows for asynchronous compute (sharing
> compute workloads between two vastly different GPUs) as well as a far more diverse set of multi-GPU
> configurations. For the first time, workloads don't *have* to be duplicated across VRAM.

Barely getting on par with Nvidia's drivers using just DX 11. And losing forward performance compatibility. (See R7-285 versus 280 in Mantle games) Mantle proved AMDs drivers were bad. It didn't prove anything else whatsoever.

In my opinion we are repeating history in full. (100%) Going back to 60s and per-HW code and quite expensive development and quite inaccessible .Then people will develop API to abstract diffs away and we will be back on square one.

> No, I don't expect the first DX12 titles to be 50% faster than DX11 games,
> but low-overhead APIs allow a lot of options that previous APIs didn't.
>
> If this wasn't the case, why would *everyone* -- Apple, Khronos, and Microsoft -- have
> cumulatively leapt for low-overhead API designs? If AMD didn't have the core of a good
> idea with Mantle, nobody would've paid attention to it. Instead we get Vulkhan based on
> Mantle and DX12 offering essentially identical features alongside Apple's Metal.

Freezing entire GPU HW for some odd reason creating new type of console out of PCs, because any new GPU will have large regressions in older DX 12 code, which won't be ready for it. Or they simply failed various historical and Theoretical Computing lessons. Pretty sure not first time nor last time several companies got blinded with some crap.

There is simply no way around, that a shade code running well on say Maxwell will be very inefficient and slow on GCN and vice versa. And in both cases any future arch will even by different ratios of TU:ROPs:L2:memory bandwidth screw things up for DX 12 code.

Too thin layer.

And I even didn't talk about stupidity of forcing devs to care about bloody memory allocation and other similar fun. (There are quite nice cases which devs will have to somehow account for yet are impossible in advance) There was a reason why DX9->DX10 transition removed that.

Nope. Generally bad idea and so far there are no sign it will be anything but bad idea with bad outcomes.