5 ms·

The Ryzens have an absurdly long branch prediction history that make them much better at repetitive tasks than random real-world workflows. I wonder how much t

• chipguy 7y ago
  That's not the impression I got from that thread. They seem to agree that this is bad for benchmarking, but remain undecided on whether that's good or bad for real-world processing. It depends on the work. So as always benchmark suites are to be taken with a grain of salt. More specific benchmarks, such as compiling a standard set of real software packages, can give a clearer picture of performance for those more specific use cases. Until we see more specific data on how these chips perform for certain tasks, this is just FUD.
  • sbov 7y ago
    > More specific benchmarks, such as compiling a standard set of real software packages, can give a clearer picture of performance for those more specific use cases. Is there a good place to go for this? I've tried to find software development focused benchmarks before, but I've come up mostly empty.
    • chipguy 7y ago
      there are many different types of benchmarks with many different CPUs/GPUs compared here: https://openbenchmarking.org/tests/pts https://openbenchmarking.org/tests/pts for a more specific example, linux kernel compilation benchmarks: https://openbenchmarking.org/showdown/pts/build-linux-kernel https://openbenchmarking.org/showdown/pts/build-linux-kernel
    • localhost 7y ago
      Phoronix is a good place to go for compilation benchmarks - https://github.com/phoronix-test-suite/phoronix-test-suite https://github.com/phoronix-test-suite/phoronix-test-suite
      • chipguy 7y ago
        The link I posted in a sibling comment is a more direct way to get to the results of that suite.
  • 3JPLW 7y ago
    Yes, that's why I qualified my "real-world tasks" with "random". What is clear is that: * Ryzen has a longer branch prediction history than Intel's processors. * This will give it an advantage on repetitive executions. * It's a challenge to robustly measure tasks since using repeated executions to gain confidence intervals can interfere with the measurement itself. What's not clear is to what extent real-world tasks are repetitive enough to benefit or random enough to be negatively impacted. It's likely a mix of both. By no means am I attempting to spread FUD — I find it quite interesting and wanted to spark a bit of discussion on it.
    • chipguy 7y ago
      Pardon. I didn't mean to imply you were intentionally doing that. Just trying to make sure there's skepticism of benchmarks as well as skepticism that the boost from branch prediction is dishonest.
• kohtatsu 7y ago
  Branch predictors sound like a good target for side-channel attacks.
  • ReverseCold 7y ago
    Well yes, that's what Spectre is.