White Paper • Version 1.8
SIMATIC PC with Intel® Core™2 Duo
simatic pc
I
• What are the advantages of dual-core
• Dual-core technology compared to
conventional processors
• What are the benefits of dual-core for
SIMATIC PCs and SIMATIC software
www.siemens.com/simatic-pc
A&D SE IPC
SIMATIC PC
“SIMATIC PC with Intel® Core™2 Duo” - White Paper
Aug. 2008
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
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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
1.4.2
1.4.3
1.4.4
2
Intel® Core™2 Duo Processors with SIMATIC PCs ...........................................14
2.1
3
Symmetrical multicore processing ............................................................................................ 11
Asymmetrical multicore processing .......................................................................................... 11
Virtualization ................................................................................................................................. 12
64-Bit Technology and its Effects on the Applications ........................................................... 13
Processors, Platforms and Technical Features of SIMATIC PCs ....................... 14
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
5
Summary............................................................................................................................ 22
Links to Further Sources and Literature ...............................................................23
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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.
Multi-core
New performance curve
through multi-core
architecture
Steeper curve, better scalability
10X
Today
Single-core
2010+
2000
Plan
Related to Intel Pentium 4 processor
®
®
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.
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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.
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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.
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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, 128bit 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
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1.3
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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.
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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.
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1.4
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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 realtime 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.
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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:
Virtualization software
(e.g. VMware, Virtual PC,
DataSynapse Gridserver)
Virtualization at the hardware
level using a hypervisor (e.g.
Linux Xen)
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
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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 32bit 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
7
Real-time operating system
One exabyte has 1018 byte, 16 EB thus comprise 16 million GB
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2 Intel® Core™2 Duo Processors with SIMATIC PCs
2.1
Processors, Platforms and Technical Features of SIMATIC PCs
SIMATIC
PC
Box PC
627B /
827B
Panel PC
677B
Processor
Clock L2(GHz) cache
Frontside
bus
(MHz)
Chipset
Graphics
TDP
(W)
VT
64
bit
HT
T5500
1.66
2 MB
667
Intel® 945
GM Express
Intel®
GMA950
34
-
3
-
T7400
2.,16
4 MB
667
Intel® 945
GM Express
Intel®
GMA950
34
3
3
-
E4300
1.8
2 MB
800
Intel® 945
G Express
Intel®
GMA950
65
-
3
-
E6600
2.4
4 MB
1066
Intel® 945
G Express
Intel®
GMA950
65
3
3
-
T5500
1.66
2 MB
667
Intel® 945
GM Express
Intel®
GMA950
34
-
3
-
T7400
2.16
4 MB
667
Intel® 945
GM Express
Intel®
GMA950
34
3
3
-
Rack PC
547B
Rack PC
847B
Fig. 3: SIMATIC PC with Intel® Core™2 Duo
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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.
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90 %
Single Core
Ardence RTX
Wind
H
MI
WinAC
RTX
Core 1
Dual Core
Dedicated
Mode
(default)
90 %
Ardence RTX
100 %
Core 2
Windows
WinAC
RTX
HMI
Fig. 4: Maximum utilization of a single-core and dual-core system by SIMATIC WinAC
0%
Single Core
100 %
Ardence RTX
WinAC RTX gets
the necessary
CPU Time
Windows
WinAC
RTX
HMI
Core 1
Dual Core
WinAC
RTX
(Default)
Windows
Ardence RTX
automatically uses
one CPU core
Core 1
RTX
„Shared
Mode“
100 %
100 % Core 2
Ardence RTX
RTX
„Dedicated
Mode“
Dual Core
High CPU Loads due to
WinAC RTX can significantly
slow down Windows'
execution and response
times.
Appl.
HMI
100 % Core 2
Ardence RTX
WinAC
RTX
100 %
Windows
HMI
Appl.
n
Appl.
m
Core Load
Fig. 5: The various installation options of SIMATIC WinAC RTX and the respectively available power reserves of the
operating system
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Windows Device Manager with a dual-core
system with SIMATIC WinAC RTX in the
standard installation (“dedicated“)
Æ only one core is visible
Aug. 2008
Windows Device Manager with a dual-core
system without SIMATIC WinAC RTX or with
SIMATIC WinAC RTX in the “shared” mode
Æ 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.
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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
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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.
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4.3.1 CPU Load
CPU load
Single-core Pentium M 2GHz
Dual-core Core 2 Duo 1.66GHz
Dual-core Core 2 Duo 2.16GHz
100%
CPU load
80%
60%
40%
20%
0%
Small visu, no archiving Small visu, archiving
Big visu, no archiving
Big visu, archiving
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.
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4.3.2 Updating Time
Updating time
Single-core Pentium M 2GHz
Dual-core Core 2 Duo 1.66GHz
Dual-core Core 2 Duo 2.16GHz
Updating time in ms
800
600
400
200
0
Small visu, no archiving
Small visu, archiving
Big visu, no archiving
Big visu, archiving
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
Screen switch & updating time
Screen switch & updating time in ms
Single-core Pentium M 2GHz
Dual-core Core 2 Duo 1.66GHz
Dual-core Core 2 Duo 2.16GHz
1600
1200
800
Considered
to be
"good"
400
0
Big visu, no archiving
Big visu, archiving
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 costfavorable) 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. Noncompliance 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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