[RC5] Power PC G4 vs. G5

Décio Luiz Gazzoni Filho decio at decpp.net
Mon Aug 1 19:35:20 EDT 2005


On Aug 1, 2005, at 8:07 PM, Ben Payne wrote:

> I have been very surprised by the relative performance of the G4  
> and the G5 processors.  I’m hoping that some people here can  
> confirm my finding and/or possibly explain why this would be  
> occurring.  I have noticed that the 7450 core is the fastest for  
> both the G4 and G5 processors.  I have also noticed that there is a  
> 970 core but it has been disabled.
>
>
>
> So here are the numbers I’m getting:
>
>
>
> I have a dual processor G5 1.8 GHz it does ~18 million keys a sec
>
> I have a 1.4 GHz mac mini that does ~15 million keys a sec.
>
>
>
> That all sound good until you add the fact that the G5 has two  
> processors and is actually clock-for-clock less than 50% the key  
> rate of the G4.
>
>
>
> G5: 18 / 1.8 / 2 = 5 million keys per sec per GHz per CPU
>
> G4: 15 / 1.4 = 10.7 million keys per sec per GHz per CPU
Have you considered the possibility that the G5 Altivec unit is  
crippled and can't hope to reach the same throughput as the 74xx's  
Altivec unit?

As far as I know, what you're seeing is perfectly normal.

Décio
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