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Are there any benchmarks that show Ryzen at 50% slower on AVX2? Intel does AVX in one clock cycle, but drastically cuts clockspeeds when AVX instructions are ex

by hajile 10y ago

Are there any benchmarks that show Ryzen at 50% slower on AVX2? Intel does AVX in one clock cycle, but drastically cuts clockspeeds when AVX instructions are executing. You'll overclock a lot, but it will then reduce the multiplier/clock the second AVX appears to keep from killing the chip. If we assume a similar AVX IPC (and Ryzen 1/2 with AVX2), you'll double your cores with Ryzen, so the AVX2 throughput per clock would be about the same. 7700 clocks higher, but then downclocks again when AVX are encountered. It seems like in practice, they are about the same for performance with AVX, but Ryzen is ahead in every other multi-threaded bench. http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/performance-xeon-e5-v3-advanced-vector-extensions-paper.pdf http://www.intel.com/content/dam/www/public/us/en/documents/...

keldaris 10y ago
There's already a few benchmarks that are directly relevant, take a look at the FFTW performance, for instance [1] (sourced from [2]), which consists mostly of single precision AVX instructions. The 1800X is handily beaten even by a deliberately downclocked 7700k, which costs a bit over half the price. But that's only half the story. The thing is, a decent 7700k (after fixing the thermal interface via delidding and using high end air or low to mid end water cooling) is actually capable of running at 4.8-5 Ghz without downclocking for AVX. You might get an unlucky sample and only do 4.6 Ghz, but it's still cost effective. A 6900k, on the other hand, doesn't have the thermal headroom to go much past its stock frequencies on AVX-heavy workloads, unless you go full crazy with sub-ambient cooling. So, in the end, it looks like the 7700k has at least double the price/performance ratio of a 1800X in AVX-heavy workloads along with vastly superior single thread performance. It looks to me like Ryzen is a great leap in price/performance only insofar as your workloads are highly multithreaded, yet don't make much use of vectorization at all. [1] http://media.bestofmicro.com/ext/aHR0cDovL21lZGlhLmJlc3RvZm1pY3JvLmNvbS8zL0QvNjU3MTkzL29yaWdpbmFsLzAxLUZGVFctMUQucG5n/r_600x450.png http://media.bestofmicro.com/ext/aHR0cDovL21lZGlhLmJlc3RvZm1... [2] http://www.tomshardware.com/reviews/amd-ryzen-7-1800x-cpu,4951-10.html http://www.tomshardware.com/reviews/amd-ryzen-7-1800x-cpu,49...

by hajile 10y ago

keldaris 10y ago

There's already a few benchmarks that are directly relevant, take a look at the FFTW performance, for instance [1] (sourced from [2]), which consists mostly of single precision AVX instructions. The 1800X is handily beaten even by a deliberately downclocked 7700k, which costs a bit over half the price. But that's only half the story. The thing is, a decent 7700k (after fixing the thermal interface via delidding and using high end air or low to mid end water cooling) is actually capable of running at 4.8-5 Ghz without downclocking for AVX. You might get an unlucky sample and only do 4.6 Ghz, but it's still cost effective. A 6900k, on the other hand, doesn't have the thermal headroom to go much past its stock frequencies on AVX-heavy workloads, unless you go full crazy with sub-ambient cooling. So, in the end, it looks like the 7700k has at least double the price/performance ratio of a 1800X in AVX-heavy workloads along with vastly superior single thread performance. It looks to me like Ryzen is a great leap in price/performance only insofar as your workloads are highly multithreaded, yet don't make much use of vectorization at all. [1] http://media.bestofmicro.com/ext/aHR0cDovL21lZGlhLmJlc3RvZm1pY3JvLmNvbS8zL0QvNjU3MTkzL29yaWdpbmFsLzAxLUZGVFctMUQucG5n/r_600x450.png http://media.bestofmicro.com/ext/aHR0cDovL21lZGlhLmJlc3RvZm1... [2] http://www.tomshardware.com/reviews/amd-ryzen-7-1800x-cpu,4951-10.html http://www.tomshardware.com/reviews/amd-ryzen-7-1800x-cpu,49...