[A51] Query - Use of Kraken with CPUs

Joel Eriksson joel.eriksson at gmail.com
Wed Mar 26 17:58:21 CET 2014


Radeon GPUs were originally made by ATI. ATI was later acquired by AMD, but
the GPUs are certainly not AMD CPUs and the performance when it comes to
the kind of computations that are required for A5/1 and crypto in general
is not even close when you compare CPUs and GPUs. The reason for this is
mainly because in a single GPU, there are actually up to thousands of cores
that performs the actual computations. In the case of Radeon HD 6990, for
instance, you have 2 GPUs that have 1536 cores each, so 3072 cores in
total. Compare that to an ordinary CPU, and you realize that a multi core
CPU does not even come close. :)

So no, it's not about using the GPU to get some extra power instead of just
letting it sit idle. GPUs are way, way faster than CPUs for this kind of
stuff. For a bit more detailed information about why this is the case, I
advise you to read this:

https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU

Quote:
"A CPU core can execute *4* 32-bit instructions per clock (using a 128-bit
SSE instruction) or *8* via AVX (256-Bit), whereas a GPU like the Radeon HD
5970 can execute *3200* 32-bit instructions per clock (using its 3200 ALUs
or shaders). This is a difference of *800 (or 400 in case of AVX) times
more instructions per clock*."

Specifically, AMD/ATI GPUs are the best suited for these kinds of
computations, which is why they are used rather than NVidia based cards.
This is because AMD/ATI cards (once again, GPUs, not CPUs ;) have a number
of features that make them well suitable for high performing integer
operations. Traditionally, GPUs are better suited for floating point
operations because that is more important for gaming/graphics performance
in general. If we take Bitcoin mining (i.e SHA-256 computations) as an
example, the Radeon HD 7970 is about five times as fast as the GTX 680.

Regards,
Joel Eriksson
clevcode.org





On Wed, Mar 26, 2014 at 5:39 PM, Nikos Balkanas <nbalkanas at gmail.com> wrote:

>
>
>
> On Wed, Mar 26, 2014 at 5:12 PM, Joel Eriksson <joel.eriksson at gmail.com>wrote:
>
>> Using CPUs instead of GPUs doesn't make any sense at all, CPUs are a
>> _lot_ slower than GPUs for these kinds of computations and you would need a
>> cluster (i.e much more expensive) to be able to get similar performance.
>>
>>
> You don't need a cluster for a multiprocessing board. Just a
> multiprocessing kernel that linux provides. Radeon's GPUs are, to my
> knowledge, AMD CPUs, but at lower frequencies. Granted, you don't have a
> general kernel running on top of them, but an MP kernel has load balancing
> and preemptive multitasking that kraken hasn't. ;-)
>
> But we are in agreement here. If you have a GPU sitting idle, why not take
> advantage of it?
>
> To really crush both CPUs and GPUs, you could create an ASIC for it
>> instead. I bet that there are A5/1 cracking ASICs out there already, just
>> not in the hands of the public AFAIK. Using FPGAs would be a decent middle
>> ground.
>>
>
> Yeap.
>
>>
>> Cheers,
>> Joel
>>
>>
>> On Wed, Mar 26, 2014 at 2:22 PM, Nikos Balkanas <nbalkanas at gmail.com>wrote:
>>
>>>
>>>
>>>
>>> On Wed, Mar 26, 2014 at 1:51 PM, Joel Eriksson <joel.eriksson at gmail.com>wrote:
>>>
>>>> It will be _a lot_ slower. If you want to have any chance of
>>>> intercepting frequency hopping calls (without having receivers constantly
>>>> recording everything at each of the possible frequencies) you need to use
>>>> GPUs and SSDs. If you don't have to deal with frequency hopping, and don't
>>>> have to decipher in near real-time, it doesn't matter as much.
>>>>
>>>> Regards,
>>>> Joel
>>>>
>>>>
>>> In such case, wouldn't it make more sense to have more CPUs on the MB?
>>>
>>>
>>>> On Wed, Mar 26, 2014 at 11:36 AM, Nikos Balkanas <nbalkanas at gmail.com>wrote:
>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Mar 26, 2014 at 8:40 AM, Amber and Sarosh <
>>>>> amber_sarosh at hotmail.com> wrote:
>>>>>
>>>>>> Hi All,
>>>>>> Can anyone please guide if GPUs are necessary for rainbow table
>>>>>> lookup using kraken to find the key to decipher an intercepted
>>>>>> communication or is it possible to do this using just CPUs? In case the
>>>>>> later is possible how much time it will take approximately?
>>>>>>
>>>>>>
>>>>> GPUs are not necessary, just desirable. If GPUs are missing, kraken
>>>>> will still work with A5Cpu.so, but it will be somewhat slower. Assuming
>>>>> that during cracking your PC is CPU limited, the benefit should scale
>>>>> roughly with your setup ratio of GPU power/CPU power. In reality you will
>>>>> run into RAM and table I/O bottlenecks before that. In short it is highly
>>>>> depended on your setup ;-)
>>>>>
>>>>> The idea is, that the easier factor to improve is the CPU, so why not
>>>>> do it?
>>>>>
>>>>> Nikos
>>>>>
>>>>>> Regards,
>>>>>> Naheed, Amber & Sarosh
>>>>>>
>>>>>> _______________________________________________
>>>>>> A51 mailing list
>>>>>> A51 at lists.srlabs.de
>>>>>> https://lists.srlabs.de/cgi-bin/mailman/listinfo/a51
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> A51 mailing list
>>>>> A51 at lists.srlabs.de
>>>>> https://lists.srlabs.de/cgi-bin/mailman/listinfo/a51
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Best Regards,
>>>>   Joel Eriksson
>>>>
>>>
>>>
>>
>>
>> --
>> Best Regards,
>>   Joel Eriksson
>>
>
>


-- 
Best Regards,
  Joel Eriksson
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.srlabs.de/pipermail/a51/attachments/20140326/3ad1745c/attachment.html>


More information about the A51 mailing list