Thursday, September 21, 2017

A11 Bionic

Srouji told me that when Apple architects silicon, they start by looking three years out, which means the A11 Bionic was under development when Apple was shipping the iPhone 6 and its A8 chip. Back then we weren’t even talking about AI and machine learning at a mobile level and, yet, Srouji said, “The neural engine embed, it’s a bet we made three years ahead.”

[…]

The high-performance cores and efficiency cores introduced with the A10 Fusion CPU got an iterative update, including the addition of two more cores and the ability to handle asymmetric multi-processing, which means the chip can run 1, 2, 3, 4, 5, or 6 cores at once. Managing the core use on the now 10-nanometer CPU is one of the reasons the A11 Bionic, according to Apple, is 70 percent more energy efficient (even while being 25 percent faster than the A10). How the system decides which cores to use (high performance or high efficiency) and how many is a little non-obvious.

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The secret sauce of a Neural Engine, what makes it different from other parts of the A11 Bionic, is its ability to handle matrix multiplications and floating-point processing.

Apple is not, however, opening this neural brain to everyone.

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There are other things the A11 Bionic controls that Apple doesn’t often talk about, including the storage controller that includes custom error-correcting code (ECC) algorithms.

This last bit relates to APFS not checksumming its data blocks.

John Gruber:

I asked Apple last week what exactly was “bionic” about the A11 chip system. The answer, translated from Apple marketing-speak to plain English, is that The Bionic Man and Woman were cool, and the A11 chip is very cool. I think they’ve started giving these chips names in addition to numbers (last year’s was the A10 Fusion) because the numbers alone belie the true nature of how significant the improvements in these chips are. Going from A10 to A11 is like going from 10 to 11 mathematically, which implies a 10 percent improvement. That’s not the case at all here — the A11 is way more than a 10 percent improvement over the A10. So they’ve given it a name like “Bionic” to emphasize just how powerful it is.

Update (2017-09-22): Mark Spoonauer (via Phil Schiller):

The “Bionic” part in the name of Apple’s A11 Bionic chip isn’t just marketing speak. It’s the most powerful processor ever put in a mobile phone. We’ve put this chip to the test in both synthetic benchmarks and some real-world speed trials, and it obliterates every Android phone we tested.

[…]

The iPhone 8 even edged out the score from the 13-inch Apple MacBook Pro with a 7th-generation Core i5 processor. That notebook notched 9,213. Is Geekbench 4 really comparable from phone to desktop? According to the founder of Geekbench, John Poole, “the short is answer is yes that the scores are comparable across platforms, so if an iPhone 8 scores higher than an i5, then the iPhone 8 is faster than the i5.”

Update (2017-10-03): David Heinemeier Hansson: