Date: Thu, 12 Jul 2012 21:13:45 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: RAdmin, SIP speedup On Thu, Jul 12, 2012 at 10:14:02PM +0530, Dhiru Kholia wrote: > On Sun, Jul 8, 2012 at 11:00 AM, Solar Designer <solar@...nwall.com> wrote: > > BTW, note that this is not a true 8-core machine (it's Bulldozer with > > its 4 modules and 2 cores per module; also it reduces clock rate from > > 4.0 GHz to 3.1 GHz or maybe slightly higher when under full load), so > > the perfect speedup would be about 6x. Thus, 3x is "only" twice worse > > than perfect. > > 4 modules * 2 cores / module = 8 cores. I don't understand why the > perfect speedup is only 6x. 3.1 * 8 / 4.0 = 6.2 Well, sometimes I get 3.2 GHz at 8 threads (with non-optimal code that does not bump into 125 W TDP at 3.1 GHz), then: 3.2 * 8 / 4.0 = 6.4 This is with FX-8120's stock settings, which are: 3.1 GHz base, 4.0 GHz max turbo, APM enabled. One thing that I find puzzling is that overclocking to 3.9 GHz base / 4.5 GHz turbo did provide some speedup at 8 threads as well, even though the TDP limit remained the same. > (In practice with OpenMP and JtR, I am seeing a speedup of ~ 4.7x on bull). There are cases of over 6x speedup as well (try the SSH format), but not much more. Alexander
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