SPEC2006 Perf: Desktop Levels, New Mobile Power Heights

Given that the we didn’t see too many major changes in the microarchitecture of the large Lighting CPU cores, we wouldn’t expect a particularly large performance increase over the A12. However, the 6% clock increase alongside with a few percent improvement in IPC – thanks to improvements in the memory subsystems and core front-end – could, should, and does end up delivering around a 20% performance boost, which is consistent with what Apple is advertising.

I’m still falling back to SPEC2006 for the time being as I hadn’t had time to port and test 2017 for mobile devices yet – it’s something that’s in the pipeline for the near future.

In SPECint2006, the improvements in performance are relatively evenly distributed. On average we’re seeing a 17% increase in performance. The biggest gains were had in 471.omnetpp which is latency bound, and 403.gcc which puts more pressure onto the caches; these tests saw respective increases of 25 and 24%, which is quite significant.

The 456.hmmer score increases are the lowest at 9%. That workload is highly execution backend-bound, and, given that the Lightning cores didn’t see much changes in that regard, we’re mostly seeing minor IPC increases here along with the 6% increase in clock.

While the performance figures are quite straightforward and not revealing anything surprising, the power and efficiency figures on the other hand are extremely unexpected. In virtually all of the SPECint2006 tests, Apple has gone and increased the peak power draw of the A13 SoC; and so in many cases we’re almost 1W above the A12. Here at peak performance it seems the power increase was greater than the performance increase, and that’s why in almost all workloads the A13 ends up as less efficient than the A12.

In the SPECfp2006 workloads, we’re seeing a similar story. The performance increases by the A13 are respectable and average at 19% for the suite, with individual increases between 14 and 25%.

The total power use is quite alarming here, as we’re exceeding 5W for many workloads. In 470.lbm the chip went even higher, averaging 6.27W. If I had not been actively cooling the phone and purposefully attempting it not to throttle, it would be impossible for the chip to maintain this performance for prolonged periods.

Here we saw a few workloads that were more kind in terms of efficiency, so while power consumption is still notably increased, it’s more linear with performance. However in others, we’re still seeing an efficiency regression.

Above is a more detailed historical overview of performance across the SPEC workloads and our past tested SoCs. We’ve now included the latest high-end desktop CPUs as well to give context as to where the mobile is at in terms of absolute performance.

Overall, in terms of performance, the A13 and the Lightning cores are extremely fast. In the mobile space, there’s really no competition as the A13 posts almost double the performance of the next best non-Apple SoC. The difference is a little bit less in the floating-point suite, but again we’re not expecting any proper competition for at least another 2-3 years, and Apple isn’t standing still either.

Last year I’ve noted that the A12 was margins off the best desktop CPU cores. This year, the A13 has essentially matched best that AMD and Intel have to offer – in SPECint2006 at least. In SPECfp2006 the A13 is still roughly 15% behind.

In terms of power and efficiency, the A13 seemingly wasn’t a very successful iteration for Apple, at least when it comes to the efficiency at the chip’s peak performance state. The higher power draw should mean that the SoC and phone will be more prone to throttling and sensitive to temperatures.


This is the A12, not A13

One possible explanation for the quite shocking power figures is that for the A13, Apple is riding the far end of the frequency/voltage curve at the peak frequencies of the new Lightning cores. In the above graph we have an estimated power curve for last year’s A12 – here we can see that Apple is very conservative with voltage up until to the last few hundred MHz. It’s possible that for the A13 Apple was even more aggressive in the later frequency states.

The good news about such a hypothesis is that the A13, on average and in daily workloads, should be operating at significantly more efficient operating points. Apple’s marketing materials describe the A13 as being 20% faster along with also stating that it uses 30% less power than the A12, which unfortunately is phrased in a deceiving (or at least unclear) manner. While we suspect that a lot of people will interpret it to mean that A13 is 20% faster while simultaneously using 30% less power, it’s actually either one or the other. In effect what this means is that at the performance point equivalent to the peak performance of the A12, the A13 would use 30% less power. Given the steepness of Apple’s power curves, I can easily imagine this to be accurate.

Nevertheless, I do question why Apple decided to be so aggressive in terms of power this generation. The N7P process node used in this generation didn’t bring any major improvements, so it’s possible they were in a tough spot of deciding between increasing power or making due with more meager performance increases. Whatever the reason, in the end it doesn’t cause any practical issues for the iPhone 11’s as the chip’s thermal management is top notch.

The A13's Memory Subsystem: Faster L2, More SLC BW System & ML Performance
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  • Jon Tseng - Wednesday, October 16, 2019 - link

    Nice! Any additional thoughts on the U1 UWB chip. I guess not much you can do with it yet but to me the possibilities are intriguing... Reply
  • Andrei Frumusanu - Wednesday, October 16, 2019 - link

    I think Apple has more plans with it in the future, but yes right now it doesn't do very much. Reply
  • tipoo - Wednesday, October 16, 2019 - link

    Definitely think it's getting the hardware ready for the AR glasses. Hyper precise location tracking just by putting your phone down on a desk and having the U1 chips communicate. Reply
  • Diogene7 - Wednesday, October 16, 2019 - link

    I am dreaming of that the Apple U1 UWB chip could be used in a not too distant future (2020 / 2021) for precise spatial locasization for at (short) distance wireless charging : by knowing where exactly in space an Apple device is, Apple might be able to dynamically and efficiently focus wireless energy transfer maybe through wireless resonant charging (Airfuel) for an iPhone or through RF charging like Energous / Ossia for recharging Apple Airpods from an iPhone...

    I think I am dreaming, but just hope that Apple is working hard to make wireless power at a short distance a reality : I would dream to be able to drop my iPhone anywhere on my bedside table, and that it automatically recharge during the night from a base station up to a distance of 1,5 foot / 50cm : it would bring sooooo much more convenience than Qi wireless charging...
    Reply
  • patel21 - Wednesday, October 16, 2019 - link

    Man, you are lazy. Reply
  • Diogene7 - Wednesday, October 16, 2019 - link

    @patel21 : How many times do you still plug an Ethernet cable to your laptop to surf on internet instead of using WIFI ? WIFI is simply more convenient...

    Similarly, wireless charging at a distance (up to ~ 1,5 foot (50cm)) would be so much more convenient than to have to plug a cable to recharge a device

    It also true for Internet of Things (IoT) devices : tjere seems to be some studies showing that consumers stop using many IoT devices that work on batteries because they have to change the batteries

    I strongly believe that wireless charging at a short distance is a requirement for the sale of IoT sensors to really take off because managing 10s or 100s or more of IoT devices with batteries is not really manageable by consumers in the long run...
    Reply
  • Henk Poley - Friday, October 18, 2019 - link

    I wonder if they'll do things like heart- and breathing-rate measurement, and counting of people around you (how many hearts). Such as was demonstrated for radar based baby monitoring. Fairly low power, a 'cigarette pack' size device attached to a baby cot could work for half a year by only periodically measuring.

    Could be interesting for meetings, that your phone knows everyone has arrived, people were agitated, etc.
    Reply
  • Adonisds - Wednesday, October 16, 2019 - link

    Why is it required less than double the power to produce twice the display brightness? Reply
  • michael2k - Wednesday, October 16, 2019 - link

    Displays aren't actually perfectly transparent, and the light generating devices might absorb some of the energy instead of transmitting it.

    Increasing transparency is one way to produce more brightness with less energy.
    Reducing the amount of energy absorbed by the LEDs (and thus transformed into heat) is another way to produce more brightness with less energy.
    Changing the LEDs basic chemistry to more efficiently transform electricity into light is a third way.

    Fundamentally less waste heat, more light.
    Reply
  • HammerStrike - Wednesday, October 16, 2019 - link

    FYI, while al other new models are rated IP68, the pro’s are listed as having a maximum submerged depth of 4 meters for 30 minutes, vs 2 for the non-pro model. Your spec comparison on the first page lists them all at 2 meters. Reply

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