Wilco (Wilco.Dijkstra.delete@this.ntlworld.com) on February 4, 2015 4:01 pm wrote:
> juanrga (nospam.delete@this.juanrga.com) on February 4, 2015 5:23 am wrote:
> > Wilco (Wilco.Dijkstra.delete@this.ntlworld.com) on February 4, 2015 1:58 am wrote:
> > > juanrga (nospam.delete@this.juanrga.com) on February 3, 2015 5:15 pm wrote:
> > > > Hugo Décharnes (hdecharn.delete@this.outlook.fr) on February 3, 2015 2:20 pm wrote:
> > > > > Cortex-A57 delivers better performances than Cortex-A15, though their micro-architectures
> > > > > are–nearly–identical. We'll see if ARM Ltd. reiterates with Cortex-A72.
> > > >
> > > > More than 80% performance gains over A57.
> > >
> > > ... but it was clearly stated that this is at the same mobile power
> > > budget. So the gains are from improved power efficiency.
> > >
> > > > ~50% IPC gain over A57, rest from ~30% higher clocks.
> > >
> > > I didn't read anything that indicated such a huge IPC gain. Peak performance should be much better of
> > > course, but much of that will be due to higher frequencies enabled by the improved power efficiency.
> > >
> > > Wilco
> > >
> > >
> >
> > I did read the preliminary analysis here
> >
> > http://techreport.com/news/27767/arm-unveils-cortex-a72-cpu-mali-t880-graphics-and-more
>
> That analysis is wrong, ignoring the fact that the comparison is at identical power, not at max
> frequency. The large gain in power efficiency allows the A72 to run at a higher frequency than
> A57 or A15, even on the same process. That means the 80% benefit is split between frequency gains
> enabled by lower power on the same process, frequency gains due to FinFet and IPC gains. Let's
> say the average IPC gain is 20% (probably not far off given the range Peter mentioned), so that
> means the frequency gain is 50% (1.5 * 1.2 = 1.8, something else Techreport got wrong).
>
> Wilco

First, thanks by the explanation.

I did just read his post and the 10--50% IPC gains, bad luck he didn't mention averages, we will have to wait to check by ourselves.