Eyebrows were raised during the iPhone 13 keynote when Apple said nothing about the A15 performance gains, choosing to compare its latest model against Android competitors rather than against the iPhone 12.

Some suggested that this indicated very little improvement in performance, but a new analysis suggests that although the A15 isn’t massively different to the A14, Apple has still managed to push the chip hard …

It had long been known that Apple would be sticking to a 5nm process for the A15 chip powering this year’s iPhones. Smaller processes are getting increasingly hard to achieve, and even next year’s iPhone lineup is expected to use a slightly smaller version of this year’s chip.

However, a deep dive by AnandTech reveals that Apple has managed to extract worthwhile performance gains by pushing the chip harder, running them at higher frequencies.

Apple’s 2021 iPhones will stick with a 5nm process, but will move to an enhanced ‘5nm+’ version […]

TSMC refers to 5nm+ as N5P, and describes it as a performance-enhanced version which will combine greater power with improved power efficiency to improve battery-life (or, as might be more likely with Apple, permit smaller-capacity batteries).

The A16 chip is expected to use what’s known as a process shrink, or die shrink, version of the 5nm+ version. Rather than being an entirely new chip process, this is a way to shrink the size of an existing chip without any major changes to its design. This gives more chips per wafer, which reduces manufacturing costs.

Apple has also doubled the system cache memory.

Microarchitecturally, the new performance cores on the A15 doesn’t seem to differ much from last year’s designs. I haven’t invested the time yet to look at every nook and cranny of the design, but at least the back-end of the processor is identical in throughput and latencies compared to the A14 performance cores [but …]

Compared to the A14, the new A15 increases the peak single-core frequency of the two-performance core cluster by 8%, now reaching up to 3240MHz compared to the 2998MHz of the previous generation. When both performance cores are active, their operating frequency actually goes up by 10%, both now running at an aggressive 3180MHz compared to the previous generation’s 2890MHz.

In general, Apple’s frequency increases here are quite aggressive given the fact that it’s quite hard to push this performance aspect of a design, especially when we’re not expecting major performance gains on the part of the new process node. The A15 should be made on an N5P node variant from TSMC, although neither company really discloses the exact details of the design.

Additionally, the performance core cache has been boosted from 8MB to 12MB, as well as reducing the latency in DRAM access.

Looking at our latency tests on the new A15, we can indeed now confirm that the SLC has now doubled up to 32MB, further pushing the memory depth to reach DRAM. Apple’s SLC is likely to be a key factor in the power efficiency of the chip, being able to keep memory accesses on the same silicon rather than going out to slower, and more power inefficient DRAM. 

GPU performance is a mixed bag.

Considering all of the changes, the site’s Andrei Frumasanu concludes that while it’s a smaller leap than usual, the A15 performance gains are still worthwhile.

In terms of peak performance, the new A15 GPU is absolutely astonishing, and showcasing again improvements that are well above Apple’s marketing claims. The new GPU architecture, and possibly the new SLC allow for fantastic gains in performance, as well as efficiency.

What’s not so great, is the phone’s throttling. Particularly, we seem to be seeing quite reduced power levels on the iPhone 13 Pro, compared to the iPhone 13 as well as previous generation iPhones.

We’re seeing increases across the board, with absolute performance going up from a low of 2.5% to a peak of +37% […]

Overall, while the A15 isn’t the brute force iteration we’ve become used to from Apple in recent years, it very much comes with substantial generational gains that allow it to be a notably better SoC than the A14. In the end, it seems like Apple’s SoC team has executed well [despite the loss of key chip design talent].