System Configurations With Distributed I/Os - Siemens SIMATIC PCS 7 System Manual

Characteristic values of redundant automation systems
A.2 Comparison of MTBF for selected configurations
Fault-tolerant CPU in stand-alone operation
Fault-tolerant CPU 410-5H in stand-alone mode
Redundant CPUs in different racks
Redundant CPU 410-5H in divided rack, CCF = 2%
Redundant CPU 410-5H in two separate racks, CCF = 1 %
A.2.2

System configurations with distributed I/Os

The system with two fault-tolerant CPUs 410-5H and one-sided I/Os described below is
taken as a basis for calculating a reference factor which specifies the multiple of the
availability of the other systems with distributed I/Os compared with the base line.
316
CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 09/2014, A5E32631667-AB
Factor
1
Factor
approx. 20
Factor
approx. 38