Date: Fri, 16 Mar 2012 01:45:23 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: AMD Bulldozer and XOP On Thu, Mar 15, 2012 at 11:24:07PM +0200, Milen Rangelov wrote: > I can help with some kernels. In fact, JtR is very inspiring project. I > like to look at how people solved similar problems often in different ways. Great. > So 256-bit XOP is slower than 128-bit one? According to benchmarks that were sent to me before I got a Bulldozer of my own, yes - about twice slower per bit (four times slower per instruction). (I haven't tested 256-bit XOP on my own FX-8120 yet. Will do so a bit later.) > This reminds me of SSE2 and some old Pentium 4 CPUs :) I think you mean SSE and Pentium 3. Yes, that was disappointing. In fact, the cause might be similar: officially, those wider registers and operations on them are "floating point" (true for both the original SSE and now for 256-bit AVX and XOP), so there might be some overhead on updating some CPU-internal floating-point state (flags reflecting the current values in the vector elements if interpreted as floating-point?) That's just a guess, though. Alexander
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.