[LBo] Performance of Multiprocessor Systems

[mars mr]

>Doubling the number of cpus will not double the
performance.


So, then why should someone say that 2 Cores, each at
1,66 is equal with 1 processor ar 3,2GHz???? 


from my tests with dual core CPUs(i`m a computer
engineer working as netowrking engineer now), i`ve
noticed that a dual core(YES both work at the same
speed, and everyone will notice that is IMPOSIBLE to
have 2 CORES in 1 processor that functions at
different speeds) is not as twice as fast than a
single core.  It usually has 50% more real processing
power, although this can vary from aplication to
aplication. 


Second:  :)

> > [Intel GHz vs. AMD Speedrating]
> > [...]
> > If you notice, server chips that are the
> > best performers only run at 1.8GHz (Xeon/Opteron)
> whereas desktop
> > processors are hitting 4GHz, but the server
> processors are obviously
> > faster.
> 
> That shows nicely that "GHz ain't everything".

Intel learned this lesson the hard way. i Think
everyone remembers the Net Burst Architecture and the
goal of Intel to be the first at 3 GHz and then at 4
GHz, dispite the real fact that an AMD chip working at
just 2,2 GHz easly beated intel`s 3,2 GHz chip in
almost every aplication possible.

The server Chips are something totally different from
normal processors. They have a huge amount of
cache(L1, L2 an L3) and speacial instructions and most
of them are specialized at a specific task, but a
workstation CPU need to do everything you need as fast
as possible.  

Although i agree they are more "faster" in terms of
processing than normal chips, they are not neccessary
at lower speeds.  I have on testing now a dual
processor(dual core each) InteL XEON at 2,4 GHz(an IBM
eSERVER series) and i`m quite happy with him, and you
can easily buy  Intel XEON at 3,2 GHz(if you have the
money). 

So basicly linux sees 4 prcessors,
2*Processor*2cores/each physical processor, but
dispite that, is not as fast as i considered. 


My Conclusion: 

As in my previous mail - a Dual Core CPU at 1,66 GHz
is not faster than a single core 3,2 GHZ(we are
talking the same architecture ..or almost the same)
since it has the same memory to access, same hdd, same
BUS(and here is the real problem). Obviously a dual
core at 1,66 GHz is faster that a singel core at the
same speed, but everyone should learn that doubling
the number of cpus(even if they are independent or on
the same phisical unit) wont double the speed, wich is
exactly what i`ve said in the last mail. 

Have fun, 



 
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