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Yeah. This was another benchmark that found that an earlier Apple CPU got impressive instructions-per-clock on a couple of cryptographic functions (that aren't
by twotwotwo 11y ago
Yeah. This was another benchmark that found that an earlier Apple CPU got impressive instructions-per-clock on a couple of cryptographic functions (that aren't special-cased like AES): https://zerobyte.io/blog/2014/04/29/benchmarking-symmetric-crypto-on-the-apple-a7/ https://zerobyte.io/blog/2014/04/29/benchmarking-symmetric-c...
But those functions also don't really stress-test branch prediction, etc. They use instruction-level parallelism but the control flow and memory accesses are predictable. (That's almost necessary for software crypto; if execution isn't ~constant-time, you risk timing attacks.)
Looking at transistor counts: Apple said the three-core A8X had three billion transistors total. Given Apple's focus on GPU and bringing other components onto the SoC, many of those are not spent on the cores; still, in raw count, it's right up there with Intel's Core-branded CPU+GPU dies, going by a table in Wikipedia.
AnandTech put up a lot of numbers about the A9, including specs like cache sizes and memory bandwidth and benchmarks like Geekbench and SPEC: http://www.anandtech.com/show/9686/the-apple-iphone-6s-and-iphone-6s-plus-review/4 http://www.anandtech.com/show/9686/the-apple-iphone-6s-and-i...
Seems like, at a minimum, if your intuitions about mobile performance come from early in-order chips, they may not apply to Apple CPUs or even the many Cortex-A57-based SoCs out there. But it also doesn't seem like you can say those chips are up there with Intel ones in general. I guess the evergreen-but-not-wrong conclusion is that to really know your code's performance, you wan to test it on hardware as similar as possible to what it'll really run on.