Peter Greenhalgh (no.delete@this.thanks.com) on February 4, 2015 11:56 am wrote:
> Hi David,
>
> Hope you are doing well.
>
> I'm going to avoid being drawn in to the discussion here, though it's great to read the speculation! :)
>
> However, I will shed some more light on some of the questions & comments
> in this thread with information we announced yesterday in San Francisco.
>
> Firstly, there are micro-architectural enhancements throughout the Cortex-A72 design which improve both
> IPC and power. In fact, the Cortex-A72 power improvements are achieved on the same process with the same
> library as Cortex-A57. We aren't relying on a process shrink to achieve the power improvement or boost
> performance purely through frequency. Depending on the workload we're seeing anywhere between 10-50%
> more clock-for-clock performance than Cortex-A57 under identical system conditions while also reducing
> power. I'm talking about a range of decent sized, representative workloads, not micro-benchmarks. More
> information on the micro-architecture and said workloads will be disclosed in due course! :)
>
> With respect to the performance uplift numbers over Cortex-A15 and Cortex-A57 that we quoted at the
> launch. These do factor in process technology. Cortex-A15 is predominantly a 28nm product, Cortex-A57
> is mainly on 20nm and Cortex-A72 we expect to see on 14nm/16nm. While the audience here on RWT is
> very technical and understands the nuances of process geometry, many of the press we speak to want
> an appreciation of how much faster the processor in their favourite phone, tablet, may be in the
> future. To that end we quote performance uplift as a combination of the IPC improvement and the extra
> frequency afforded to our silicon partners due to advances in process technology.
>
> Overall we're extremely pleased to have increased IPC while meaningfully decreasing power
> across various use cases. It's going to be great to see Cortex-A72 in partner platforms.
> As we've got more than 10 partners extremely active with the processor I hope the wait
> won't be too long! [in a big.LITTLE configuration with Cortex-A53 of course ;)]
>
> I'm going back to lurk-mode now.
>
> Best Regards,
>
> Peter Greenhalgh (Director of Technology, CPU Group, ARM)
>
Thanks very much for those details. The ipc gain sounds very worthwhile but what I find particularly impressive is the huge power requirement reduction. That is far better than could be expected from the process change and must have taken a lot of design effort.