john-users - Re: john improvement suggestions

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Date: Wed, 21 Dec 2005 20:57:09 +0100
From: Simon Marechal <simon@...quise.net>
To: john-users@...ts.openwall.com
Subject: Re:  john improvement suggestions

Solar Designer wrote:
> On some CPUs, ALU+SSE, MMX+SSE, and even ALU+MMX+SSE could be beneficial,
> too - and people have been doing that.  There's definitely room for
> improvement here.

MMX and SSE are the same physical registers (with FPU too) on my athlon 
xp, and AFAIK, this is true for the other architectures too:

	mov $0x4444, %eax
	movd %eax, %mm0
	pxor %xmm0, %xmm0
	movd %eax, %mm1
	paddd %mm1, %mm0
	movd %mm0, %eax

eax will have the value 0x4444
if the "pxor %xmm0, %xmm0" line is removed, it will be 0x8888

I do not think it is possible to use at the same time MMX+SSE effectivly.

The main problem with using ALU+(MMX/SSE) is that x86 processors are 
register starved.

However there is definitly room for improvement on amd64.

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