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SIMATIC PC “SIMATIC PC with Intel® Core™2 Duo” - White Paper Aug. 2008

Copyright © Siemens AG 2007 A&D AS / SE All rights reserved 2 of 23

Purpose: This white paper is to: - clarify the question as to the advantages offered by two processor cores; - present special features of the Intel® Core™2 Duo; - explain technical terms; - describe the behavior of dual-core processors with SIMATIC software. Note: The information contained in this documentation merely contains general descriptions and performance characteristics which may not always be applicable in the described form to the specific application case or may change due to product advancement. The desired performance characteristics shall only be binding if they are expressly specified upon contract conclusion. Editor Siemens AG Automation and Drives P.O.Box 2355 90713 Fuerth Germany Further support Provided by Siemens contact partners at your local representations and branches SIMATIC PC on the Internet

Information on SIMATIC PC on the Internet: www.siemens.com/simatic-pc Your local SIMATIC partners are listed at: www.siemens.com/automation/partner Siemens A&D Mall for configuring and ordering your individual SIMATIC PCs: www.siemens.com/automation/mall



Contents

Introduction ............................................................................................................................4

1 Design and Function of Multi-Core Processors ....................................................5 1.1 Processor Development Stages .................................................................................... 5

1.1.1 Single-Core Processor.................................................................................................................. 5 1.1.2 Single-Core Processor with HT Technology.............................................................................. 5 1.1.3 Dual-Core Processor..................................................................................................................... 6

1.2 Dual-Core Processor Technology Exemplified with Intel® Core™2 Duo Processor......................................................................................................................................... 6

1.2.1 Technical Terms pertaining to Intel® Core™2 Duo.................................................................. 7 1.2.2 Advancement of Intel® Core™ Duo to Intel® Core™2 Duo ................................................... 8

1.3 Advantages of Multi-Core Technology ........................................................................ 9 1.4 Different multicore systems.......................................................................................... 11

1.4.1 Symmetrical multicore processing ............................................................................................ 11 1.4.2 Asymmetrical multicore processing .......................................................................................... 11 1.4.3 Virtualization ................................................................................................................................. 12 1.4.4 64-Bit Technology and its Effects on the Applications ........................................................... 13

2 Intel® Core™2 Duo Processors with SIMATIC PCs ...........................................14 2.1 Processors, Platforms and Technical Features of SIMATIC PCs ....................... 14

3 Intel® Core™2 Duo Processor Technology with SIMATIC WinAC.................15 3.1 Operation of the Realtime-Capable SIMATIC WinAC RTX Software PLC on Single- and Dual-Core Systems ............................................................................................... 15

4 Performance Comparisons of SIMATIC WinAC RTX and SIMATIC WinCC flexible on Core™ 2 Duo and Single-Core Processor ...............................................17

4.1 Objective of the Tests and Test Platforms................................................................ 17 4.2 Used Software Configurations ..................................................................................... 18 4.3 Tests and Test Results................................................................................................... 19

4.3.1 CPU Load ..................................................................................................................................... 20 4.3.2 Updating Time .............................................................................................................................. 21 4.3.3 Screen Switch Time .................................................................................................................... 22

4.4 Summary ............................................................................................................................ 22 5 Links to Further Sources and Literature ...............................................................23



Introduction

Up to now, mainly the processor’s clock frequency was increased when it came to improving the performance of computing systems. However, an increased clock frequency always entails an increased current input and thus an increased waste heat in the form of thermal power loss (TDP, thermal design power). This waste heat, which ranges above 100 W with the current single-core processors, could almost no longer be dissipated by the previous heat sinks operated with fans in accordance with the specified enclosure dimensions and ventilation options. Even though the progress in processor production allows for ever smaller processor designs (the current state of production being the 65 nanometer (!) – procedure), which consume less current and thus produce less waste heat, an increased clock frequency would again nullify this TDP reduction. Furthermore, also technical and physical obstacles, which cannot always be solved, impede such reduction.

Fig. 1: Development of processor performance This situation led to the development of multi-core processors, which no longer increase the system performance via a mere increase of the clock frequency, but through the integration of several processor cores on a chip. In addition, several processes allow for the parallel execution of program commands and thus increase the processing speed of programs. This accommodates the current requests for more complex and interdependent programs (e.g. software PLC and corresponding visualization).

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1 Design and Function of Multi-Core Processors

1.1 Processor Development Stages

1.1.1 Single-Core Processor

Single-core processors until 2002: Every PC was equipped with exactly one processor – so-to-speak the heart which drove the computer. The operating speed indicator used to be stated in megahertz, a measurand which has meanwhile been replaced by gigahertz. The biggest problem with these conventional processors is that they can only process one task (thread) at a time, no matter how high their clock rate is.

Since the eighties, it has been possible to combine two or more processors to assemble a multi-processor system with the required hardware (motherboard). Based on this principle, the Pentium was the first processor by Intel which facilitated the realization of multi-core systems also for private users. However, such computers were not as fast as could be assumed by addition of the individual clock rates alone (i.e. two 3 GHz processors on one motherboard did not add up to a computing power of 6 GHz). Amongst others, the memory connection, which was not fast enough back then to supply both processors with sufficient data, turned out to be a bottleneck. Moreover, the programs were not designed to utilize the available cores as the employment of multi-core processor systems was rather uncommon at the time.

1.1.2 Single-Core Processor with HT Technology

Since 2002, Intel® Pentium® 4 processors have been supporting hyper-threading technology1 and are classified as processor with two cores by the operating system. However, as they can still only execute tasks with one real core, HT does not nearly increase the performance to a level as can be attained by the installation of two processors.

1 Hyper-threading technology (HT technology) simulates a further processor and thus accepts two tasks from the operating system like a real dual-core processor and then transfers these tasks to the core’s CPU. If the programs are optimized for execution via several threads, hyper-threading supports a speed increase of up to 20 %. Hyper-threading is also available with some multi-core processors; dual-core processors with HT technology are correspondingly equipped with 4 cores.



1.1.3 Dual-Core Processor

Dual-core processors accommodate two fully fledged CPUs – in one enclosure. At best, dual-core processors operate

twice as fast with some applications as the single-core variants. At worst – when a program is written to only support processing via a single thread – no performance increase will be noticeable. This program would then actually only benefit from an increased clock frequency. Nevertheless, the power reserves of the second core are additionally available even in this case, enabling the user to

run further applications on this core.

1.2 Dual-Core Processor Technology Exemplified with Intel® Core™2 Duo Processor

A dual-core processor consists of a single chip on which two computing units, so-called cores, are combined. With an Intel® Core™2 Duo processor, both cores operate with a jointly used memory, the so-called level-2 cache2. At best, this cache is filled with the data next required by the processor, which are calculated with the help of a jump prediction program. With Intel® Core™2 Duo, both computing cores operate with a joint, dynamically managed 2 MB or 4 MB L2-cache with Intel® Smart Cache functionality (see next page), which facilitates additional acceleration. All current Intel® Core™2 Duo processors are equipped with the Enhanced Intel® SpeedStep® (EIST) power saving technology to dynamically adjust the processor clock rate to the current requirements. With Siemens SIMATIC PCs, this function is deactivated as the maximum processor performance is always guaranteed in any case! The Execute-Disable-Bit function (XD-Bit), which can prevent the execution of malware (certain types of viruses and trojans), is also implemented. To use this function, it has to be supported by the operating system, e.g. Windows XP with Service Pack 2, and activated in BIOS by the customer.

2 Level-2 (L2) cache – particularly fast memory still on the processor but no longer on the processor core itself (which is the level-1 cache). In this memory, the last used data which will very probably be accessed again are saved. This way, access to the “slow” main memory is minimized. At best, the processor sources all data required for processing from this memory. The cache memory in general is employed wherever the speed of memory access has a particular impact on a system’s performance.



1.2.1 Technical Terms pertaining to Intel® Core™2 Duo • Intel® Wide Dynamic Execution

With the core micro-architecture, Intel has improved the capacities for dynamic code execution. Wide Dynamic Execution supports up to four instructions per processor clock pulse per core – as opposed to hitherto maximally three.

An improved jump prediction and larger buffers allow for the execution units’ continuous feeding.

With the help of the “macro-fusion“ function, frequent instruction sequences can be merged to a process-internal command, called micro-op, during the decoding step. This increases the number of instructions per clock cycle. Furthermore, the micro-op fusion function known from the Pentium M was expanded to a larger number of micro-ops. All in all, this technology enhances the processor’s utilization. At the same time, the workload is reduced as a program can be executed in fewer processor cycles.

• Intel® Intelligent Power Capability

A particularly fine division of the chip in partitions and functions which can be rapidly addressed facilitates an accurate adjustability to current requirements. The core micro-architecture only activates the actually required chip partitions while all other partitions remain switched off. This saves power and thus reduces the waste heat with low utilization. In addition, numerous buses and fields of the processor are split and only the required bandwidths are used. The processor benefits from proven technologies such as Enhanced Intel® Speedstep® and particularly deep sleeping states.

• Intel® Advanced Smart Cache

This cache variant is optimized for application in multi-core processors. For this purpose, the entire L2-cache (up to 4 MB, depending on the Intel® Core™2 Duo processor) is jointly used by the computing cores. Assignment is realized dynamically on the basis of the utilization principle. This way, the entire memory can be provided to one core if this core is highly utilized, while it evenly serves both cores in case of balanced utilization. The cache size used by the individual core thus varies according to requirements and may amount to up to 100 percent. In addition, a core can access the data of the other core already saved in the cache when identical datasets are processed. Synchronization of the caches via the processor’s front-side bus is dropped. After all, the bandwidth was increased towards the processor with the Advanced Smart Cache, which further improves the performance.

• Intel® Smart Memory Access

This feature increases the system performance with the help of several technologies through an optimized utilization of the available bandwidth towards the memory. The “Memory Disambiguation“ feature, for instance, facilitates the optimization of memory accesses. Furthermore, this function attempts to predict and calculate which memory accesses can be executed before others. With the help of so-called prefetchers, the processor analyzes memory accesses in advance. If the prefetchers are right, the data are already available in the fast L2-cache when required and the processor can immediately continue operation without first having to load the data from the “slow” RAM.



• Intel® Advanced Digital Media Boost For the acceleration of multimedia applications, the core micro-architecture processes 128-bit wide SSE instructions3 in only one clock cycle. Before, 128-bit wide SSE instructions used to be executed in two steps – first the last 64 bits, then the first ones. With only one clock cycle for a 128-bit SSE instruction, the throughput for applications using SSE is significantly increased. This comprises video, image and sound processing, coding and technical-mathematical applications.

1.2.2 Advancement of Intel® Core™ Duo to Intel® Core™2 Duo The Intel® Core™2 Duo processor is the improved version of the Intel® Core™ Duo processor. The Intel® Core™2 Duo processor offers a performance increase of roughly 12% compared to an Intel® Core™ Duo processor, with a slightly higher power consumption. Currently, the Intel® Core™2 Duo processors for notebooks employed in Siemens SIMATIC PCs have a power input of TDP = 34 W, while an Intel® Core™ Duo processor in the notebook variant has a TDP of 31 W. The Intel® Core™2 Duo technology supports the Intel® 64-bit architecture, also known as EM64T, a functionality which was not incorporated in the predecessor version. Also the above-described macro-fusion function for the generation of micro-ops, which is to be of benefit for roughly every tenth command, is a new feature of the Intel® Core™2 Duo architecture.

3 SSE = Streaming SIMD (Single Instruction Multiple Data) Extension; instruction set for the accelerated processing of programs through parallelization



1.3 Advantages of Multi-Core Technology Software:

The full performance potential can only be utilized if the used operating system and software are programmed to use the processor’s available cores. However, many applications – particularly older ones – are still designed for only one core. As long as only this application runs on a PC, it does not benefit from multiple processor cores. The higher clock frequency of a single-core processor thus offers an advantage in this case. Yet, as soon as several programs/threads run in parallel, the number of processors becomes noticeable. Whether applications can distribute their calculations to several processors depends on their multithreading capability. This term refers to a software’s capability of distributing functions and executing them in parallel in so-called threads. Windows NT has been capable of addressing several processors since 1993. With regard to current operating systems, for example Windows XP SP 2 or higher and its successor Vista are designed for operation on multi-core systems.

Fig. 2: Hyper-threading with dual-core processors facilitates the parallel execution of 4 threads

However, even if the applications on a computer are not designed for multi-threading, advantages become noticeable as soon as several programs are to be executed simultaneously. For example, virus protection could run on one core, while a Word document is edited or a video played on the other core without any delays. This allows for cost-favorable future overall solutions by enabling users to combine control and visualization in a single system. New solutions are facilitated, with which one core with integrated realtime control is active and thus executable while the other core, e.g. executing a visualization software, can be rebooted. Further applications comprise remote access, e.g. for remote maintenance with firewall, an Industrial Ethernet link via a further core. etc.

Hardware:

The combination of two or more processor cores on a single die4 offers the advantages of a multi-core system while maintaining the infrastructure of a single-core system. The new technology supports an improved computing power and thus allows for the realization of more complex and demanding solutions with the same number of computers.

4 A “die” is a small semiconductor plate containing the microprocessor (core) (see image): With dual-core processors, two cores are accommodated on one die.



The employment of Intel® Core™2 Duo processors and special power-saving features facilitated a significant performance improvement with a non-linear increase of waste heat and power demands. The reduced power input of the latest generation of Intel® Core™2 Duo processors allows for smaller, lighter and yet more effective cooling systems, which smoothly fit into the available enclosures and thus facilitate installation compatibility. Low waste heat is a must for compact systems. In addition, well-cooled processors offer a considerably longer service life than their counterparts operated in the limit range. Alternatively, computers can be operated at considerably higher ambient temperatures with unchanged service life, which extends their application range.



1.4 Different multicore systems

1.4.1 Symmetrical multicore processing

In symmetrical multicore processing systems (SMP), the hardware resources are assigned dynamically. An installed operating system has access to all resources. This type of system architecture has been the standard architecture of all multiprocessor systems for approximately 20 years. Benefits result from simple handling for users since they usually do not have to make any settings or changes to the programs. The drawback of this architecture is,

for example, the heavy load on the memory bus that has to provide the data for the processors. Another disadvantage results from CPU hopping in which the individual processes of a program are alternately distributed to different cores. This leads to performance losses due to varying cache accesses in each case. The more processor cores are available, the more marked are the disadvantages.

1.4.2 Asymmetrical multicore processing

In asymmetrical multicore processor systems (AMP) each of the different cores is assigned its own hardware resources. An operating system installed on a core can only access the hardware resources assigned to it. Direct communication between the individual operating systems is not possible, but must be implemented using additional interfaces (IPC – Inter Process Communication). Completely different operating systems are typically used on one computer in AMP

systems. The benefit of this solution is that the installed operating systems can be optimized for high-performance execution of their respective tasks. For example: a visualization system on an operating system like Windows or Linux can run in parallel with a real-time operating system for controlling a machine. A disadvantage is the restricted functionality of the operating systems resulting from permanently assigned hardware. It may be necessary to make adaptations within the operating system in order to optimize it to the task in hand.



1.4.3 Virtualization Virtualization means several operating systems can run on one computer simultaneously, but separately. The high-end versions (T7400 and E6600) of processors installed on SIMATIC PCs support the Intel® Virtualization Technology VT ("Vanderpool"). This accelerates the emulation of operating systems such as Windows, whose source codes are not openly accessible. There are two different types of virtualization:

Software virtualization: Virtualization at the software level simulates interfaces and hardware peripherals and requires computing capacity on the processor to do so. Software virtualization is thus correspondingly "slow". However, standard operating systems such as Windows XP can be used. Operating systems are loaded, removed and backed up in the same way as programs. Different operating systems can also be virtualized provided the virtualization software allows this. The behavior of a newly developed program block on a computer can thus, for example, be simulated in a virtualized environment before its actual implementation. Hardware virtualization: Virtualization at the hardware level exhibits greater performance efficiency because it involves installation of only rudimentary software called a hypervisor5 or virtual machine monitor (VMM; e.g. Linux Xen) that provides the most essential coordination functions. This VMM can assign hardware resources to a virtualized operating system. Virtualization at the processor level has the advantage of being faster compared with software virtualization. In addition, operating systems can be loaded independently of each other, or removed from the computer in the case of damage. If an operating system is attacked by hackers or viruses, it can be deleted and reloaded from a secure instance. Only operating systems that support the same processor architecture (e.g. x86) can be used. Solutions are possible in which a real-time operating system, for example, runs on one core, while Windows runs on the other.

5 An "operating system for operating systems" as it were

Virtualization software (e.g. VMware, Virtual PC, DataSynapse Gridserver)

Virtualization at the hardware level using a hypervisor (e.g. Linux Xen)



The prospects for virtualization options: It is expected that virtualization technology will radically alter existing and future IT infrastructures. Virtualization allows users to create low-cost overall systems by, for example, integrating control and visualization on a single system. Solutions can be envisaged in which one core with integral real-time control is active and can thus be executed, while the other core, running visualization software, for example, can be rebooted. Or an RTOS6 running a control hosts a guest OS with visualization, and limits or expands the computing capacity of the visualization system depending on the utilization of the controller. In this way, the visualization system and the control can make optimal use of the resources on a powerful PC, and the higher priority of the controller is provided at all times by the separation into host and guest OS. Envisaged are, for example, workstations that do not require their own computer because they use the network to access a server that starts a virtual OS for each user. Here, the benefits for companies are to be found in IT cost savings thanks to reduced requirements for devices, cables, accessories, etc. The available computing power can also be better distributed among the individual users. Word processing typically leaves a large proportion of capacity unused on a workstation computer. Hypervisors, on the other hand, can assign computing power as required. If program errors are encountered, a simple restart of the virtual machine is usually the remedy, thus avoiding time and cost-intensive phone calls to IT coordinators or help centers. Finally, it only remains to mention that programs do not have to be adapted when a changeover to new hardware becomes necessary – at least, not while virtualization solutions for emulating the old operating system are available to the new hardware. Such systems are also less susceptible to computer viruses: when they attack system files, the viruses disappear when the virtual OS is restarted. Or a programmer programs a new tool for an application. The development environment runs on an OS on one core, while the OS with the application program runs on another core, so developers can immediately test their new software blocks. Other applications include remote access, e.g. remote maintenance with firewall, an Industrial Ethernet link via another core, and much, much more.

1.4.4 64-Bit Technology and its Effects on the Applications For servers, 64 bit have meanwhile become the standard, while 32-bit applications and operating systems are still widely spread in industrial environments. The Intel® Core™2 Duo architecture allows for the execution of 64-bit applications. As a prerequisite for fully utilizing the 64-bit architecture, it has to be supported by the operating system, e.g. the 64-bit versions of Windows XP or Vista. 64-bit architecture means an expansion of the variables and addresses to 64 bit. A further restriction of the 32-bit architecture is the maximum memory size of 4 GB RAM, which can be addressed linearly. If more than 4 GB RAM are employed in a 32-bit computer, the memory exceeding the 4 GB cannot be addressed. This restriction is eliminated by the 64-bit architecture, allowing for a utilization exceeding the 4 GB memory by operating systems (theoretically up to 16 EB7). This new architecture is particularly advantageous for memory- and/or data-intensive applications and for programs which have to execute complex calculations with high numerical values. To operate Windows in the 64-bit variant, it has to be ensured that all drivers are available in a 64-bit variant as they cannot be installed otherwise.

6 Real-time operating system 7 One exabyte has 1018 byte, 16 EB thus comprise 16 million GB



2 Intel® Core™2 Duo Processors with SIMATIC PCs

2.1 Processors, Platforms and Technical Features of SIMATIC PCs

SIMATIC PC Processor Clock

(GHz) L2-cache

Front-side bus (MHz)

Chipset Graphics TDP (W) VT 64

bit HT

T5500 1.66 2 MB 667 Intel® 945 GM Express

Intel® GMA950 34 - - Box PC

627B / 827B

Panel PC 677B T7400 2.,16 4 MB 667 Intel® 945

GM ExpressIntel®

GMA950 34 -

E4300 1.8 2 MB 800 Intel® 945 G Express

Intel® GMA950 65 - -

Rack PC 547B

E6600 2.4 4 MB 1066 Intel® 945 G Express

Intel® GMA950 65 -


Intel® GMA950 34 - -

Rack PC 847B


Intel® GMA950 34 -

Fig. 3: SIMATIC PC with Intel® Core™2 Duo



3 Intel® Core™2 Duo Processor Technology with SIMATIC WinAC

As described in Chapter 1.3, current operating systems can utilize the capacities of the dual-core processor technology. However, to reach the maximum speed, also the executed programs have to support parallelization. In industrial environments, not only the maximum attainable performance is relevant, but also a “minimum” guaranteed performance is of the essence to ensure a predictable system behavior. When the SIMATIC WinAC RTX software PLC is used with a dual-core processor, a system can be realized which provides a predictable performance both for SIMATIC WinAC RTX as well as for the Windows XP part.

3.1 Operation of the Realtime-Capable SIMATIC WinAC RTX Software PLC on Single- and Dual-Core Systems An installation of SIMATIC WinAC RTX on a dual-core system differs from that on a single-core system as follows (see illustrations on the next page): SIMATIC WinAC RTX on a single-core system On a normal single-core system, the realtime expansion of SIMATIC WinAC RTX utilizes the performance it requires (max. 90%) to execute the code. To meet the realtime requirement, a safety reserve has to be used in this case. This may lead to significant (permanent or short-term) restrictions of the Windows performance. SIMATIC WinAC RTX in the “dedicated mode” on a dual-core system When SIMATIC WinAC RTX is installed on an Intel® Core™2 Duo system with Windows XP, the realtime expansion of SIMATIC WinAC RTX reserves a complete core of the processor as a standard. For the Windows operating system, one CPU core remains visible and thus available. No safety reserve has to be considered here due to the division to respectively one separate core. The realtime application and visualization each operate with 50% of the performance in this case. SIMATIC WinAC RTX in the “shared mode” on a dual-core system If more resources are required for Windows, the Ardence RTX core used by SIMATIC WinAC RTX can also be configured in a way which ensures that only part of a CPU core is used to make both CPU cores visible and thus available to Windows.



Ardence RTX

WinACRTX

Wind

HMI

Single Core90 %

Ardence RTX Windows

HMIWinACRTX

Core 1 Core 2

Dual CoreDedicatedMode (default)

100 %90 %

Ardence RTX

WinACRTX

Wind

HMI

Single Core90 %

Ardence RTX Windows

HMIWinACRTX

Core 1 Core 2

Dual CoreDedicatedMode (default)

100 %90 %

Fig. 4: Maximum utilization of a single-core and dual-core system by SIMATIC WinAC

Ardence RTX

Core Load

WinACRTX

Windows

HMI

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WinAC RTX getsthe necessaryCPU Time

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(Default)

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Ardence RTX automatically usesone CPU core

Ardence RTX Windows

HMIWinACRTX

Core 1 Core 2

Dual Core

RTX„DedicatedMode“

(Default)

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Ardence RTX automatically usesone CPU core

High CPU Loads due to WinAC RTX can significantly slow down Windows' execution and response times.

Windows

HMI

Ardence RTX

WinACRTX

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Dual Core

RTX „Shared Mode“

Appl.n

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100 %100 %

Windows

HMI

Ardence RTX

WinACRTX

Core 1 Core 2

Dual Core

RTX „Shared Mode“

Appl.n

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Fig. 5: The various installation options of SIMATIC WinAC RTX and the respectively available power reserves of the operating system



Windows Device Manager with a dual-core Windows Device Manager with a dual-core system with SIMATIC WinAC RTX in the system without SIMATIC WinAC RTX or with standard installation (“dedicated“) SIMATIC WinAC RTX in the “shared” mode

only one core is visible both CPU cores are available

Fig. 6: Varying representation of the processor with installed WinAC in the Windows Device Manager

Compared to a single-core processor system, this layout ensures that every operating system, Ardence RTX of SIMATIC WinAC RTX on the one hand and Windows XP on the other hand, is assigned to a separate processor core. This way, the operating system has sufficient reserves to prevent bottlenecks – e.g. caused by a visualization software with an archiving system or by a performance-intensive machine vision application – right from the start.

4 Performance Comparisons of SIMATIC WinAC RTX and SIMATIC WinCC flexible on Core™ 2 Duo and Single-Core Processor

4.1 Objective of the Tests and Test Platforms To illustrate the differences between single-core and dual-core and the power reserves of an Intel® Core™2 Duo system, a software PLC and a visualization were used as a basis – a software constellation typical for PC-based automation solutions. The hardware is connected via PROFIBUS. SIMATIC WinAC RTX as PC-based S7 control delivers the acquired data and variables to the SIMATIC WinCC flexible visualization software. Additional applications or hardware integrated on the Windows side are quite common today, with an upward trend for the future. As various applications may be based on significantly differing constellations and accordingly varying performance requirements, detailed results would bear small relevance for the practice. This is why such differences are not considered here in favor of a simplified illustration. The description of the used configurations is correspondingly short. Due to the focus on “minimum performance” for the Windows side, SIMATIC WinAC RTX was operated with the “standard installation”, i.e. in the “dedicated mode” (see Chapter 3.1). The comparison measurements can only be seen relatively in correlation with the comparison devices due to the software and hardware constellations. An individual value in itself bears little significance as all measurements contain cycle times of SIMATIC WinAC RTX, data exchange from SIMATIC WinAC RTX to SIMATIC WinCC flexible, etc. All indicated times are averaged values.



As test platforms, three SIMATIC PC systems, one with single-core and two with respectively differing dual-core CPUs, were compared: • Single-core platform SIMATIC Panel PC 677 / Box PC 627:

Intel® Pentium M 760 processor with 2.0 GHz • Dual-core platform SIMATIC Box PC 627B / Panel PC 677B:

Intel® Core™2 Duo T7400 processor with 2.16 GHz and Intel® Core™2 Duo T5500 with 1.67 GHz

As operating system, Windows XP Professional MUI (SP2) was used. Via the integrated PROFIBUS interface of the SIMATIC PCs, a SIMATIC ET200S is connected as distributed I/O to set external triggers in the system.

4.2 Used Software Configurations The following SIMATIC software was installed for the tests:

• SIMATIC WinAC RTX 2005 in the “dedicated mode”

o The used S7 program and the SIMATIC WinAC configuration mainly serve the generation of a constant CPU basic load of 90% and the pass-through of I/Os for time measurement from PROFIBUS to SIMATIC WinCC flexible.

• SIMATIC WinCC flexible 2005 Runtime o Use of two different visualizations, a “small” and a “big” one. Implementation

of simple calculations and display of variables, in the small visualization <20, in the big visualization >400. The minimum updating time is configured in SIMATIC WinCC flexible.

o For the connectable “archiving”, SIMATIC WinCC flexible scripts and a Microsoft SQL server are used. The scripts are called up every 100 ms and generate two tables with respectively newly calculated values, which are then written in an SQL database.

Small visualization, few variables Big visualization, very many variables

Fig. 7: View of the small and big visualization



4.3 Tests and Test Results To identify the performance differences, the following tests were implemented (the test results are shown on the following pages): • CPU load

o Measurement of the CPU load on the Windows side via the Windows Task Manager.

• Screen switch time o Time required for changing and completely updating all values in a SIMATIC

WinCC flexible screen. • Updating time

o Time from switching of a digital input to representation on the SIMATIC WinCC flexible visualization.

• SIMATIC WinAC RTX execution time o The execution time of the SIMATIC WinAC RTX program was measured. The

used program mainly serves the assurance of a constant CPU basic load. This results in a high similarity of the cycle execution times with the three test systems – the CPUs have a comparable single-core performance with similar clock frequencies. The measured cycle times of the systems range very closely to each other and within the tolerance range of the measuring instruments used for this test. These cycle times are not explained further and have only little impact on the test results.

The test results are graphically illustrated on the following pages. The determined values are average values of individual measurements.



4.3.1 CPU Load

Fig. 8: CPU load of Windows XP with the various SIMATIC WinCC flexible test scenarios

During normal operation, the test scenario on a dual-core system hardly exceeds a utilization of 20% (no screen change or the like), providing approximately 80% CPU power reserves. Additionally running applications can thus respond significantly faster. In contrast, on the single-core system, the basic load of the test scenario already leads to a considerable utilization of the Windows system. With the test scenario including archiving, the single-core system already shows a utilization of almost 100% and thus responds more slowly to user entries and causes a delayed screen representation.

0%

20%

40%

60%

80%

100%

CPU

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Small visu, no archiving Small visu, archiving Big visu, no archiving Big visu, archiving

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4.3.2 Updating Time

Fig. 9: Updating time of the various SIMATIC WinCC flexible visualization scenarios

Actions causing an additional load on the system, changes in the visualization, screen changes, mouse movements, etc., generate a high-priority load in the Windows system, which decelerates the transfer of data (here an external trigger signal) from SIMATIC WinAC RTX to SIMATIC WinCC flexible to the display on the screen. The dual-core systems are able to raise this required computing power via the free CPU reserves. Single-core systems rapidly meet their performance limits and slow down the execution of requests. Even though frequently all applications can still be operated, the “assumed performance” is slower due to the longer updating time.

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4.3.3 Screen Switch Time

Fig. 10: Screen switch time of the various SIMATIC WinCC flexible visualization scenarios

In this example, the influences of additional system loads are clearly visible. The screen switch time, i.e. the time until a new SIMATIC WinCC flexible screen with all variables is refreshed, ranks in very good ranges with the dual-core systems. The fast Intel® Core™2 Duo CPU is twice as fast as the smaller 1.67 GHz computing unit. With the single-core system, the screen formation is considerably slower and the complete system responds with a noticeable delay. In the measurement scenario, SIMATIC WinCC flexible also triggered fault messages due to overload. The results of the screen switch times with small visualizations are not shown as the systems all show a very similar screen formation which ranges on the limit of the measurable times.

4.4 Summary The new dual-core systems offer considerable performance reserves for applications which exhaust the performance limits of current systems or for cases where applications have to be cut back on due to restricted performance. This is clearly illustrated by the example of the “big visualization” with numerous variables which have to be continuously re-calculated and displayed. When further decelerated by archiving functions, the – actually fast – single-core CPU reaches its performance limits. The advantage that a separate processor core can be assigned to the software PLC provides Windows with a defined performance (“a CPU”) independent of the realtime part’s load. For practical applications, this means that the Intel® Core™2 Duo PCs with Windows used here can be extended by further integrated applications (e.g. machine vision or archiving systems, etc.), which can serve as the basis for an innovative (and cost-favorable) overall solution for the future.

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5 Links to Further Sources and Literature

Intel® Core™2 Duo at Intel: http://www.intel.com/cd/products/services/emea/deu/processors/core2duo/300415.htm Intel® Core™ Duo at Intel: http://www.intel.com/products/processor/coreduo/index.htm Chipset Intel® 945GM Express at Intel: http://www.intel.com/products/chipsets/945gm/index.htm Intel® Core™ website with many further links to detailed feature descriptions of the Core™ architecture (white papers): http://www.intel.com/technology/architecture/coremicro/ Presentations from the “Entwicklerforum Multicore-Processing 2006“ (developer forum multi-core processing 2006): http://www.elektroniknet.de/index.php?id=1304&type=98

Brands All product designations may be brands or trademarks whose utilization by third parties for their purposes may violate the rights of the owners. Copyright © Siemens AG 2007; all rights reserved Any transmission and reproduction of this document, as well as any utilization and disclosure of its contents shall not be permitted, unless expressly approved. Non-compliance will result in claims for damages. All rights reserved. Disclaimer We have verified the contents of this brochure for compliance with the described hardware and software. Yet, we cannot exclude any deviations and can therefore not guarantee complete compliance. The data contained in this brochure are regularly verified and necessary corrections are included in the subsequent issues. We would be thankful to receive your improvement suggestions. Subject to changes.

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simatic pc I - Home - English - Siemens Global WebsiteD SE IPC I SIMATIC PC with Intel® Core 2 Duo simatic pc Whi te P aper • V ers i on 1. 8 • What are the advantages of dual-core