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I am interested in the Intel Xeon E5-1650 v3 and the Intel Xeon E5-2643 v3 processors. They both have 6 cores and a clock speed of ~3.5GHz. However, the specifications from CPU-world (screenshot) show that the Intel Xeon E5-2643 v3 processor has 2 multiprocessing units as opposed to 1 for the Intel Xeon E5-1650 v3. I am aware of what the difference is between cores and threads, although I am confused why one of the processors has 2 multiprocessing units and the other only 1. What does this mean in practical terms?

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    This is a information field that CPU World has created. The only technical field from intel's specification it could be is the Scalability, even then, Intel offers no insite what Scalability means. Comparison of both. I suggest contacting CPU World for clarifiacation on their report. – Ramhound Jul 6 '15 at 14:48
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    I believe based on what I'm seeing in your post, and Ramhound's comparision on ARK (which is really the only place to go for intel questions) is that its a reference to QPI links, which among other things, allow two processors in seperate sockets to work together on modern systems. the E5-1650 v3 has 0 QPI links, so it can support one processor with no QPI. The second chip has 2 QPI links so it can use up to two sockets. en.wikipedia.org/wiki/Intel_QuickPath_Interconnect – Frank Thomas Jul 6 '15 at 14:58
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    That might be what Intel means by Scalability in other words, the E5-2643 v3 can be placed in a motherboard with 2 sockets. Honestly only CPU World can fully explain what that field means. – Ramhound Jul 6 '15 at 15:04
  • even the wikipedia entry on QPI is dense, but this quote explained a lot for me: "LGA 1156 Core i3, Core i5, and other Core i7 processors from the Lynnfield/Clarksfield and successor families) do not expose QPI externally, because these processors are not intended to participate in multi-socket systems. However, QPI is used internally on these chips to communicate with the "uncore", which is part of the chip containing memory controllers, CPU-side PCI Express and GPU" en.wikipedia.org/wiki/Intel_QuickPath_Interconnect – Frank Thomas Jul 6 '15 at 15:07
  • Theres also the "Max CPU Configuration" on ARK, that matches the numbers on CPUWorld. but that would be too clear a title... – Frank Thomas Jul 6 '15 at 15:09
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The "Multiprosessing" in this case refers to Symmetric Multiprocessing (SMP).

This is when you have more than one physical processor on the motherboard.

The first number in the second section of the Intel model number tells you the maximum SMP configuration the processor can be part of. So for example, E5-1650, it's a "1" and with E5-2643 it's a "2".

The E5-1650 cannot be used in an SMP configuration, and the E5-2643 can be used in an SMP configuration with (up to) 1 other processor (2-way SMP), and something like the E5-4620 can be used with up to 3 other processors for 4-way SMP.

Here's an link to a comparison of these three CPU's at Intel's ARK (see the line titled "Max CPU Configuration"):

http://ark.intel.com/compare/85758,81900,82765

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