Wednesday, September 18, 2013

Anandtech Benchmarks Apple's 64-Bit A7 SoC

Anand Lal Shimpi over at Anandtech has just weighed in on Apple's 64-bit A7 SoC. Anand is widely acknowledged as the leading expert on CPUs and GPUs among tech writers and reviewers on the web today. You should really read the entire article, but I'm going to focus on his analysis of the A7 and its CPU (code named Cyclone).

Anand believes that the CPU consists of two 64-bit ARMv8 cores with a max frequency of 1.3 GHz. Integer performance for 32-bit code has increased 42% from last year's A6 to this year's A7. Running 64-bit code on the A7 increases integer performance by another 38% (the A7 can run code in both 32-bit and 64-bit mode). This yields an overall increase of 95%. For floating point performance, the corresponding increases are 67%, 36%, and 128%.

Geekbench 3.0.0 Compute Performance
Integer (ST) Integer (MT) Floating Point (ST) Floating Point (MT)
Apple A6 1.3 GHz
(32-bit code)
750 1472 588 1165
Apple A7 1.3 GHz
(32-bit code)
1065 2095 983 1955
Apple A7 1.3 GHz
(64-bit code)
1471 2872 1339 2659

Some of the increases in integer performance can be attributed to new cryptographic instructions for hardware acceleration in the ARMv8 instruction set, but it is fairly clear that Apple has, once again, taken the lead in both CPU and GPU performance. It briefly held the lead last year when it released the A6, but it was quickly overtaken in CPU performance by incremental improvements to Qualcomm's Snapdragon SoC.

I expect Apple to hold onto the CPU performance crown a little longer this year. Qualcomm is still trying to squeeze more performance out of its Snapdragon SoC, but the LG G2 just came out a week ago with Qualcomm's latest and greatest, and it doesn't come close to the iPhone 5s. Meanwhile, Samsung and Nvidia are both using ARM's Cortex-A15 (although Samsung has recently taken an architecture license), which was really designed by ARM for the server market and not the mobile market. It runs extremely hot. Apple absolutely destroys the competition in terms of performance per watt and IPC (instructions per cycle), and its competitors won't be able to catch up by increasing core counts and max frequencies any more. They are all hitting thermal ceilings.

This means that we won't see a credible competitor for Cyclone and the A7 until someone else releases an ARMv8 core. Samsung bragged that they'll have one in 2014. I'm sure that Qualcomm has something in the works, but they haven't announced anything, yet. Like the Cortex-A15, ARM designed the 64-bit ARMv8 instruction set with the server market in mind, and ARMv8 cores for the server market aren't even predicted until 2014.

And this is ignoring the software side completely. Anand confirms that all of iOS and all of Apple's iOS apps are already 64-bit. At boot up, there isn't a single 32-bit process running on the iPhone 5s. That is astonishing. The transition from 32-bit to 64-bit took a lot longer on OS X. In fact, there are a number of key Apple applications on OS X that are still 32-bit.

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