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Entry type: FAQ, Entry ID: 42650, Entry date: 04/21/2008

What is multicomputing mode and what are the differences to operating in the segmented subrack?

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The properties and advantages of multicomputing:

  • Common K bus and common P bus in non-segmented module racks (central controllers) URL and URL.
  • All CPUs work on one common I/O and communication bus, with automatic synchronization of the operating state transitions.
  • A complex overall task can be split over up to 4 CPUs.
  • Scalable performance increase is possible by simple slotting another CPU.
  • Increase of system resources (memory, flags, counters, ...).
  • Option of separating time-critical process part from non-time-critical process parts (e.g. rapid control of a fast closed-loop controller).
  • Every I/O module is assigned to one specific CPU.
  • Multicomputing is supported by S7-400 CPUs with the following order numbers:
Module Order number: Order number: previous / discontinued
CPU 412-1 6ES7412-1XJ05-0AB0 6ES7412-1XF01-0AB0
CPU 412-2 6ES7412-2XJ05-0AB0 6ES7412-2XG00-0AB0
CPU 414-2 6ES7414-2XK05-0AB0 6ES7414-2XG01-0AB0
CPU 414-3 6ES7414-3XM05-0AB0 6ES7414-3XJ00-0AB0
CPU 414-3 PN/DP 6ES7414-3EM05-0AB0  
CPU 416-2 6ES7416-2XN05-0AB0 6ES7416-2XK00-0AB0
CPU 416F-2 6ES7416-2FN05-0AB0 6ES7416-2FK04-0AB0
CPU 416-3 6ES7416-3XR05-0AB0 6ES7416-3XL00-0AB0
CPU 416-3 PN/DP 6ES7 416-3ER05-0AB0  
CPU 416F-3 PN/DP 6ES7 416-3FR05-0AB0  
CPU 417-4 6ES7417-4XT05-0AB0 6ES7417-4XL00-0AB0
Table 1: Modules that support multicomputing

Operation in the segmented module rack CR2

  • The CPUs in the segmented module rack are each an independent subsystem and behave each like a separate processor, i.e. there is no multicomputing.
  • The segmented module rack contains two separate P bus segments with 10 slots in Segment 1 and 8 slots in Segment 2.
  • For each I/O bus segment one CPU is implemented, to which the I/O modules are assigned locally. The CPUs work independently of each other without synchronization of the operating state transitions.
  • The common communication bus enables communication of subunits without additional hardware.
  • Two separate controllers can thus be realized in one CR (space saving in the switchgear cabinet).
  • Cost saved, because only one module rack and one power supply are required.

More information on this topics is available in

  • Entry ID: 1117849 "SIMATIC S7-400 Programmable Controllers Hardware and Installation (installation manual)", section 2.3.
  • Entry ID: 23904550 "SIMATIC Automation System S7-400 CPU Specifications", section 3.1.

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