Re: Dual Core vs. Dual CPU

On Sun, 23 Apr 2006, Urs Thuermann wrote:

> I'd like to know what is the difference between a system with a dual
> core CPU compared to two (single core) CPUs.  I know dual core means
> two CPUs on one chip, but is it really two complete CPUs or do they
> share some component which is used by both CPU cores?

In the case of AMD, the processors, L1 and L2 cache are replicated for a 
dual-core chip.  But the hypertransport to get off-chip is not 
replicated, nor is the memory controller.  So there could be a 
bottleneck on the dual-core that two single-cores don't have.

But then there is price.  The dual-core system will be cheaper than the 
dual cpu system...




>
> For example HT duplicates only those parts of CPU which hold the state
> of the program in execution (i.e. program counter, registers, etc.)
> but they share the execution logic which often leads to performance
> loss.
>
> Is there some performance difference between dual core and two real
> CPUs, too?  I assume the dual cores on one chip must share the bus
> interface, but since in a multi CPU system only one CPU can access the
> bus at a time, I think this doesn't make a performance difference,
> right?
>
> Can anybody give some clarifiactions on these issue?
>
> urs
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