AMD Phenom 6-core vs Opteron 8 and 12 core

[incurablegeek]

In what way would the user benefit from a jump from a 6-core with 3.2 GHz. to an 8 or 12 core running at a lowly/slowly 2.0 GHz? 

I do know that:

1) Server (Opteron) chips are much more thoroughly tested than desktop (Phenom) chips.
2) You must be sure to optimize each of the Opteron (server) cores so they are all running at a full 2.0 GHz and not system-idle speed of I believe 800 MHz.

Bottom Line?  Is anything above 6 cores just for bragging rights or are the 8 and 12 core chips worth the money?

[DMHolt57]

In a multicore system, multiple cores often perform calculations that involve the same chunk of data. As long as the data is still required by some core, it shouldn't be deleted from memory. So when a core begins to work on the data, it ratchets up a counter stored at a central location, and when it finishes its task, it ratchets the counter down. The counter thus keeps a running tally of the total number of cores using the data. When the tally gets to zero, the operating system knows that it can erase the data, freeing up memory for other procedures.

As the number of cores increases, however, tasks that depend on the same data get split up into smaller and smaller chunks. The MIT researchers found that the separate cores were spending so much time ratcheting the counter up and down that they weren't getting nearly enough work done. 

[incurablegeek]

I remember a similar argument several, several years ago when motherboards that handled two processors were criticized because the second processor resulted in only a 20% increase in speed.  Now, having very little social life at the time    , I have occasionally been reduced to loading 1, 2 and 3 programs (5 DVD conversions maxed out a 6 core) just to watch which cores were active, when and by which programs.  On my 6 core they all stay pretty active - in relatively decent parity.

So regarding my core question of Phenom 3.0 GHz vs Opteron 2.0 GHz, what do you think the reasons are for the dramatic difference in speed and what impact would that have on performance?

++++++++

Now for a fly in the ointment, how about this addendum:

If an AMD 8-core opteron running at 2.0 GHz is really two 6-cores with a total of 4 cores disabled,

1) What is the way to unlock those 4 cores and have a 12 core?  (I know it has been done on lesser core chips)

2) There are many reasons why the Opteron 8 and 12 cores run at only 2.0 GHs (compared to a 3.0-3.2 Phenom).  Is one of the reasons they run at such a slow speed the fact that those 8 cores could contain disabled cores (4) that failed ASUS' testing?

Now I know I am really, truly a certifiable PITA, but you sir have a bit more CPU architecture knowledge than I do - so I'm gonna try to learn as much from you as I can.

DMHolt57, I so appreciate your response.  Thanks much. 

[DMHolt57]

At the present state of architecture, we are limited in the consumer pc market by growing pains, some facets of hyperthreading with more and more cores also produces slower results.  In two to five years we will look back and say...wow, we were really in the dark ages, it may not be about the max number of cores, but more about multiple levels of flash memory...  

[incurablegeek]

Bottom Line: No discernible difference between my AMD 6-core at 3.2 GHz. and an Opteron 8 core at 2.0 GHz?

Just a waste of money for senseless bragging rights?

    (I have noticed that my Phenom II 6 core is faster than my Phenom II 4 core.)