32/64 bit AMD question

[Russell Cook]

On Tue, 2005-10-18 at 14:10 -0400, Lewis Futrell wrote:
> From: Russell Cook [mailto:bike_oz at yahoo.com.au] 
> Sent: Tuesday, October 18, 2005 8:04 AM
> To: Ubuntu Help and User Discussions
> Subject: 32/64 bit AMD question
> 
> 
> 
>  
> 
> Maybe put another way, what is the performance difference in 64 bit
> mode compared to 32 bit, of the 754 pin and the 939 pin AMD Athlon64's
> for the same clock speed?
> 
> 
> 
> The funny thing is, it is exactly the memory interface that is
> different between the two.  The 754 socket only does single channel
> memory (64 bit path) whereas the 939 CPU’s are dual channel (128 bit
> path).  The 64 bit part of the processor is the same.  The performance
> difference will be the memory bandwith.
> 
> 

Thanks Lewis, does that mean that in 32bit mode the chip only does 32bit
memory accesses but in 64 bit mode the 754pin chip does 64 bit and 939
pin chip does 128bit (memory access not calculations)?

If true, then 64 bit mode should be faster than 32bit in both chips, but
the 939 will be faster (by the memory access time) then the 754. Do I
have this understanding correct or am I still missing something?

Regards Russell.
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