[RC5] RC5-72 G5 core

Didier Levet kakace at wanadoo.fr
Sun Oct 31 08:23:50 EST 2004


Le 31 oct. 04, à 13:18, Jonas Maebe a écrit :

>
> On 31 Oct 2004, at 08:11, Per Hallström wrote:
>
>> The G5 processor has been available for a long time now, and the 
>> fastest RC5-72 core is still slower (per GHz) than on the G4.
>
> The G5 is simply slower per MHz/GHz than the G4. For some 
> applications, this is offset by the larger memory bandwidth, but rc5 
> doesn't care about that. Of course, the G5 also scales much better 
> MHz-wise than the G4.

The G5 is actually slower than expected due to a higher lantency 
between dependant instructions (2 clock cycles vs 1 on G4).

>> Is there any optimization work in progress? Are there any plans at 
>> all for an improved G5 core?
>
> I don't know. It's of course possible that there are ways to improve 
> the keyrate on the G5, but it would surprise me if you could ever get 
> a keyrate per MHz comparable to a G4.

A G5 could be 30% faster at RC5, but that'd require a very complex 
piece of code to work around the latency issues mentionned above. By 
now, nobody was able to write this new core.

Didier.



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