Frequently Asked Questions - FAQs
General on organization
The PCI Industrial Computers Manufacturer's Group, PICMG, is a consortium of more than 400 companies who collaboratively develop open specifications for high performance telecommunications and industrial computing applications. The members of the consortium have a long history of developing leading edge products for these industries. Further information is available at http://www.picmg.org .
PICMG Europe is an
independent association with a mission to make CompactPCI visible within Europe
through the neutral promotion of member’s products and by expounding the available plethora of commercial
PCI local bus components and introduce them to the non-office environment where
robust form factor and harsh operating conditions
prevail. Through active promotion of the pioneering work of the
association, PICMG Europe reviews and approves new specifications that reflect
the changing market within the European Union. Further
information is available on this website http://www.picmgeu.org
.
3.
What is the PCI
SIG – Special Interest Group?
All manufacturers (more than 800 at
present) of PCI hardware, no matter if desktop, notebook, industrial PCs, or
embedded computer, are organized in the PCI-SIG (Peripheral Component
Interconnect – Special Interest Group), which among other things supervises
the compliance with the bus standard. Further information is available at
www.pcisig.org.
4.
What
other specifications has the PICMG issued?
The
first effort of the PICMG was to publish a specification for passive backplane
computers using both PC style (card edge connector) ISA and PCI bus. This was
completed in early 1995, and is generally known as the "PCI-ISA Passive
Backplane" specification. The PICMG has also issued a specification for PCI
to PCI bridges which allow passive backplane computers to extend the number of
PCI slots. Both of these specifications are explained elsewhere on this web
site. The CompactPCI project began in 1994, with the first formal specification
approved in November of 1995.
General
on CompactPCI
CompactPCI is a computer bus to connect different functional units (boards) to provide a system. Today, in modern computers the PCI bus is used as de-facto standard for these connections. The PCI bus can be considered as the successor of the ISA bus, as included in the original PC of the 1980’s, with drastically improved features, such as 32/64-bit data capacity and 33/66 MHz bus clock. Thus, transfer rates of 132 MByte/s (32 Bit / 33 MHz) or 528 MByte/s (64 Bit / 66 MHz) are possible.
In contrast to desktop computers or notebooks, which often provide all features on one board, CompactPCI computers are composed of several plug-in cards of the Eurocard size (100 x 160 mm). The cards have an accessible panel on the front side and connectors at the rear side (J1, J2: socket connectors), allowing to plug the modules onto a bus backplane (P1, P2: plug connectors). The CompactPCI backplane provides all PCI signals and the power supply signals.
In a CPU module both connectors (J1, J2) are always mandatory. I/O modules with 32 Bit bus access only require J1. When Rear I/O is used, J2 is also necessary to connect this. I/O modules with 64 Bit always require J2.
CompactPCI stands for mechanical reliability, easy accessible and maintainable, clever cooling philosophy, compactness and modern bus interfaces as well. Besides the mechanical “differences”, CompactPCI modules have an electrically advanced connector. This lifts the limit of PCI modules within one system up to the reasonable maximum of 16 modules.
Thus, the Compact
PCI bus is considered as the industrial variant of the PCI bus standard.
2.
What is the CompactPCI bus?
CompactPCI
is a very high performance industrial bus based on the standard PCI electrical
specification in rugged 3U or 6U Eurocard packaging. Unlike its desktop cousin,
the CompactPCI board uses a high quality 2 mm metric pin and socket connector
that meets IEC and Bellcore standards. CompactPCI boards are inserted from the
front of the chassis, and I/O can break out either to the front or through the
rear.
The
CompactPCI effort was initiated in 1994 by Ziatech Corporation under the
auspices of the PCI Industrial Computer Manufacturer's group (PICMG). The
CompactPCI specification is the result of a concerted effort of the CompactPCI
subcommittee composed of the following companies: Digital Equipment, GESPAC,
I-Bus, Pro-Log, Teknor, Hybricon, and Ziatech.
4.
What
are the unique features and benefits of CompactPCI?
Compared to standard desktop PCI, CompactPCI supports twice as many PCI slots (8 versus 4) and offers a packaging scheme that is much better suited for use in industrial applications. For example, Compact PCI cards are designed for front loading and removal from a card cage. The cards are firmly held in position by their connector, card guides on both sides, and a face plate which solidly screws into the card cage. Cards are mounted vertically allowing for natural or forced air convection for cooling. Finally, the pin-and-socket connector of the CompactPCI card is significantly more reliable and has better shock and vibration characteristics than the card edge connector of the standard PCI cards. The power and signal pins on the CompactPCI connector are staged so as to allow the specification in the future to support hot swapping, a feature that is very important for fault tolerant systems and which is not possible on standard PCI. Also, 6U CompactPCI supports 3 additional 2mm connectors with a total of 315 pins. These can be used for secondary buses (like SCSA or MVIP telephony buses), bridges to other buses like VME or SCSI, or for user I/O. User I/O can be routed out the back of a 6U card and out the back of the chassis, a practice popular in the telecommunications industry.
5.
What applications
are targeted by CompactPCI?
CompactPCI
is intended as an industrial bus for application in telecommunications, computer
telephony, real-time machine control, industrial automation, real-time data
acquisition, instrumentation, military systems or any other application
requiring high speed computing, modular and robust packaging design, and long
term manufacturer's support. Because of its extremely high bandwidth, the
CompactPCI bus is particularly well suited for many high speed data
communication applications such as servers, routers, converters and switches.
Although as yet incomplete, a hot swap feature has been planned for in the
CompactPCI specification which will be particularly well suited for the
telecommunication industry.
6.
For which
applications is CompactPCI appropriate?
Due to the variety of modules, the CompactPCI bus is ideally suited for systems
- which do not fit on one module, so based on a modular structure,
- which should be extendable in the future (modular approach)
- which demand a great deal of maintainability, or
- which have to sustain particular environmental conditions.
Due to the modular structure, the systems can be customized so that larger quantities can cost-efficiently be provided.
7.
What other applications could benefit from CompactPCI?
CompactPCI
can benefit all applications requiring very high data transfer rates. Data
communication interfaces such as ATM and broadband ISDN are good examples. In
the field of high energy physics research, very fast multi-channel data
acquisition cards will benefit from CompactPCI. Many of the most exciting
applications are probably yet to be invented, but if history is any indication,
the sophistication of systems will increase to use all available computing
bandwidth that CompactPCI computers have to offer.
8.
Is
CompactPCI a real standard that is accepted worldwide?
Yes, it is. The PICMG http://www.picmg.org defines the CompactPCI standards. The PICMG consists of members. These include suppliers and users from all over the world. It is active since around 10 years now, and CompactPCI is now at a stable release 3.0. In addition it is supported by 100’s of suppliers with 1000’s of products, used in numerous applications and markets.
A European organization was founded besides
the American PICMG – PICMG Europe (http://www.picmgeu.org)
– due to the large number of hardware developers. PICMG US and
9.
Which Operating Systems can CompactPCI computers run?
Pentium
based CompactPCI computers can run all operating systems that have ever been
ported to the PC, including MS-DOS, Windows 3.11, Windows 95, Windows NT,
VxWorks, OS/2, SCO and BSD UNIX, LINUX, Novell Netware, IntranetWare, OS-9000
and QNX. PowerPC based CompactPCI computers will be able to run AIX, SOLARIS,
Windows NT, Mac OS and OS-9.
10.
What
are the software implications of PCI and CompactPCI?
The PCI
architecture, developed by Intel, has been carefully planned to simplify the
software integration of a peripheral device. For example, all PCI or CompactPCI
device have a set of 256 registers which contain information on the device
identity, as well as a great deal of software programmable parameters such as
address maps, or interrupt types and levels. As a result, the system CPU can
automatically detect and identify a device on the bus and configure it without
the need for jumpers on the peripheral. PCI is a key element of the "Plug
and Play" concept. CompactPCI is truly a "systems level" bus,
with configuration (plug and play) and hardware abstraction layers. This permits
a high level of software portability, common in the desktop PC world but much
rarer in embedded systems.
11.
What are the
system implications of CompactPCI?
Every
modern computer architecture has an internal PCI bus, whether or not it supports
PCI add-on slots (which it usually does). This is the case for nearly all
Pentium PCs, Alpha workstations, and PowerPC systems based on the PREP or CHRP
reference platform standard. CompactPCI makes it possible to build any computer
compliant with these hardware system designs. As a result, CompactPCI systems
can be built using standard components and can run practically any operating
system and thousands of application software packages without modification.
CompactPCI
– a layered approach
12.
What
software is available for use with CompactPCI
As
far as application and operating systems are concerned CompactPCI does not
differ from the standard PC. This is the third advantage. Every type of software
and every operating system running on a standard PC is also applicable on
CompactPCI.
13.
What
differences between PC and CompactPCI are relevant for software developers?
It should be impossible for software developers to discover any differences between the CompactPCI computer and a standard PC above the driver level.
However, exceptions apply, due to enhancements of modules making them more suitable for industrial applications, like watchdog timers, and system management function.
14.
Will
CompactPCI system run real-time operating systems well?
The
performance of CompactPCI is particularly well tuned to real-time application,
from machine control to machine vision, fast data acquisition and data
acquisition. Operating systems like OS-9, PSOS, VxWorks run very well on
CompactPCI hardware and will be instrumental in the expected success of
CompactPCI in these markets.
15.
Where
can I learn more about PCI technology in general?
There is
a great deal of information on the web published by the PCI SIG, which is the
organization responsible for desktop PCI standards. You can learn more about the
SIG's activities by contacting www.pcisig.com.
There is a Frequently asked Questions section that can be reached at www.pcisig.com/support/faq/index.php3.
16.
What future
developments are likely for CompactPCI?
As of
April 1996, several technical subcommittees have been formed to expand the
definition of the bus. They include:
·
Hot Swap
·
CompactPCI Bridging (more than 8 slots) - Recommended Practices
·
VME-64 Extension (allows the construction of hybrid CompactPCI/VME
systems)
·
TDM (Computer Telephony) Buses on P2 (including MVIP and SCSA)
Also, a
"Pin Registry" is being developed to detail recommended practices for
using the upper three connectors on 6U boards for I/O. For example, PICMG has
developed recommended practiced for IndustryPack and PMC pinouts on the
additional connectors.
17.
How can I
get a copy of the CompactPCI Specification?
You can
order a copy through the PICMG Europe website http://www.picmgeu.org
. PICMG Europe members receive a free copy of the specifications and updates.
Several short forms are
available on this web site. You can get a membership application by filling in
the membership subscription form on the PICMG Europe website.
CPCI
Markets
1.
Are
CompactPCI products prone to early obsolescence?
No.
Unlike the desktop PC market which is driven by volume and fast changing
consumer demand, CompactPCI is driven by professional customers who value
product stability and long term availability. All major CompactPCI manufacturers
have at least 10 years of experience each serving the OEM marketplace and have
established reputations for protecting their customers from the dangers of early
obsolescence. This is achieved by a careful selection of components and their
suppliers, and even, in many cases, by stocking several years worth of demand of
key components.
2.
Can
CompactPCI offer me a long-term availability?
Yes, it can, but the question needs to be answered in two ways. The question of availability concerning the underlying future technology can clearly be answered with “yes”. Modules for computers will be PCI modules in the foreseeable future. Even the future distribution of serial bus systems, such as PCI Express, will not influence this fact. This reminds of those technologies whose near end was already predicted one decade ago such as the ISA bus (see PC/104) as well as discussions whether the CompactPCI bus replaces the VME bus.
The second part of the question refers to whether your supplier can offer CompactPCI on a long-term basis. Besides financial stability of a company, and long-term interest to support this, the open bus approach helps here too – functions can be exchanged with similar products of other suppliers, extending the scope and life-cycle.
3.
Are CompactPCI products
expensive?
No. Even
though they offer unprecedented performance, they are based on broadly available
silicon implementation produced in very high volume. This high volume silicon
has the highest performance/price ratio available because of the economies of
scale. Additionally, because the PCI bus is not terminated, no external bus
drivers are required to interface a PCI peripheral. An Ethernet controller, for
example, connects directly from the leads of the controller chip on to the PCI
connector. CompactPCI products are typically priced below equivalent VME product
but slightly above desktop PCI products.
4.
Is
CompactPCI appropriate for use in systems with complex I/O?
CompactPCI
systems are especially appropriate in this area. Systems with 500 digital and
analog inputs and outputs are easily and reliably realized via the mechanical
and electrical integration capability of peripheral cards. Additionally, the
computer can be integrated into a fieldbus structure via master and slave
interface modules.
In general: If your system demands for more I/O modules, more communication, more complexity and more computing power, it leads you to CompactPCI systems.
5.
Is CompactPCI
appropriate for industrial use?
At the end of the sixties the Eurocard size
with indirect plug-in was developed especially for industrial applications.
Since then it was invariably used. It provides the setup of finely modular
systems, simple extensibility in the field, outstanding mechanical resistance
even in situations of shock and vibration, and best maintainability. Systems
such as SMP16 and VME are using those advantages even after decades.
The second important advantage is somewhat hidden, but essential for the functioning over a long period of time. Eurocards are indirectly interconnected via a gas-proof connector in which every signal is connected by a pin/socket combination. This connection can be compared to a connector in a power outlet. Thus, this plug-in contact is vibration and acceleration resistant, gas-proof, and therefore protected against ambient air. The contacts made of gold cannot contaminate and corrode. Today, the demand for safe contacts is indispensable because of predominating low voltages and currents as well as high signal frequencies.
In contrast to that PCs are equipped with a direct plug-in-mount. Prongs are directly fixed on the motherboard, without additional connectors. Springs in a receptacle are pressed on those prongs. In most cases PC cards need front and rear prongs. During accelerations or decelerations (or vibrations with both) one spring relaxes while the other is tightened. It is easy to produce minor failures.
If the system is not mechanically stressed,
dust and humidity will cause corrosion on prongs and springs. There is no danger
of corrosion as long as the card is fixed: The direct plug-in is still gas-proof
at the contact prong (gold) / contact spring (beryllium gold). Problems only
arise if the plug-in card is disconnected after a long time. A new one needs to
be inserted or similar changes of the “well-rehearsed” prong/spring team are
necessary. You surely know: Never touch a running system. However, in case of
Compact PCI systems with indirect plug-in mount this is possible, even after
many years.
Experts assure that the mechanics and
connectors are the preconditions for industrial computers. In addition, various
safety and diagnostic features (Watchdog, voltage and temperature monitoring,
alarm outputs, light-emitting diodes LED), EMC resistance and immunity as well
as electrical separation also belong to modules for industrial application.
6.
When
should I use CompactPCI in my application instead of a standard PC?
A standard PC is the more competitive solution in case it should be used as an individual system that does not have to be reproduced. Another criterion is the estimation of damage in case of failure.
Although the opposite is strongly stated, a life time cost assessment is at best rudimentarily done even though the keyword “Total Cost of Ownership” is well known. The technical inferiority of standard PCs in an industrial environment has to be estimated for the particular application.
We all know standard applications that have to be maintained over a long period of time, and where real-time applications depend on the hardware as well as the BIOS version, and where spare parts have to be available for years or decades. This has been the classic application of 19” industrial computers for over 30 years.
Equipped with modern processors and having a performance that ranks on a high level, the CompactPCI system stands in this tradition.
7.
Are
CompactPCI systems available for the transportation sector, like vehicles?
Yes,
because of the mechanical superiority of the 19” Eurocard technology. This
computer technology with CompactPCI bus is virtually predestined for vehicle
applications. Possibilities of modules and systems, like booting from
CompactFlash, and vehicle compatible energy supply, make CompactPCI systems the
first choice in mobile IT.
8.
Why
are CompactPCI boards / components more expensive than standard PC components?
Due to the mechanical and electrical design a CPCI system is more expensive than a standard PC. The quantity can never keep up with the mass production of standard PCs today.
There is actually only a slight difference between a standard PC and an industrial computer with motherboard. Have you ever calculated the costs for the system’s lifetime over 10 years? Consider advantages like easier upgrades of the system, modularity, simpler spare inventory and better services in case of failure?
It
is proved to be “difficult” to buy the identical PC again 5 years later. In
many real time systems the new BIOS release is enough to run the application. In
this case the initial cost for a CompactPCI system proves to be the more
beneficial investment.
9.
Is
it true that CompactPCI is already technologically obsolete?
A
new initiative, named PICMG EXP.0 has started with a new specification in order
to integrate PCI Express into a CompactPCI standard allowing that they can
coexist with existing systems. This specification has the purpose of fulfilling
future market necessities of 3 U CompactPCI, PXI, military and aerospace. The
specification will define plugs as well as electrical and mechanical
requirements of 3 U system slot boards, peripheral boards, switch boards and
backplanes. It is assumed that this specification will influence also 6 U boards
and backplanes. The mechanical change of CompactPCI format resulting from this
specification only refers to the plugs. It is not intended to deviate from the
mechanical guidelines of the CompactPCI specification.
10.
Which products are
available on CompactPCI?
CompactPCI
Pentium and PentiumPro systems are available from a variety of suppliers in a
variety of packages. System level add-on function such as 100 Mbit/s Ethernet,
fast SCSI, accelerated VGA, image acquisition, and analog and digital I/O, ATM,
FireWire and FibreChannel communications, motion control, and PMC and
IndustryPack (IP) carriers are currently available. Other companies have
announced plans for PowerPC CPU boards, fast fiber optics networks, image
acquisition and processing, and a host of other I/O.
Technical
issues CPCI
1.
What
is the difference between a CompactPCI industrial PC and an IPC with
motherboard?
An IPC with motherboard is a standard PC with a 19” enclosure. This is comparable to a Sport Utility Vehicle (SUV). A SUV is not able to pull a plough even though it is an off-road vehicle.
The problem of direct plug-in inside as described above is not solved in the case of an IPC with motherboard. The mounting of standard PC plug-in cards is solved within the scope of the limited possibilities of non-standardized PC card dimensions. In addition, the critical component “power supply” is not sufficiently considered.
In case of service the IPC has to be dismounted and opened before getting through to the plug-in card. Compared to CompactPCI, the advantages are lower costs, due to the use of mass-market components.
The
customer has the choice: Is a standard PC enough for the application, is a 19”
enclosure necessary, or do you require higher reliability and serviceability
which only a CompactPCI system can fulfill?
2.
What
processors can be implemented on CompactPCI?
Although
PCI has gained most of its recognition as a local bus for 80x86 based PCs, PCI
is at the core of all modern microprocessor designs. PowerPC and DEC's Alpha,
for example, are supported with chip sets with PCI interfaces and can be easily
implemented on CompactPCI. In fact, CompactPCI is the industrial bus that does
the most justice to these very high performance new chips, giving them a system
bus with all the bandwidth that these chips are capable of.
3.
Can I have
more than 8 slots in a CompactPCI system?
Yes.
Each CompactPCI bus is limited to eight slots for electrical loading reasons.
This can be easily expanded with PCI-PCI bridge chips, available from a number
of manufacturers. The bridge chip acts as a sort of "super buffer"
chip. Interrupts, plug-and-play information, and data are easily and generally
automatically transferred across the bridge. A bridge chip usually exacts a one
clock penalty ( generally about 30 nanoseconds) per transaction. If the data
transaction is a burst mode type - transferring hundreds or thousands of bytes
at a time - this overhead is extremely small. One advantage of bridge chips is
that each side of the bridge can be performing data transfers to cards on its
side of the bridge simultaneously.
4.
What
is Rear I/O technology?
One of the advantages of CompactPCI is the high contact density of its connectors J1 and J2. They provide far more signals on the backplane than actually necessary for the PCI bus. Serial interfaces, Ethernet channels, USB terminals, fan control or warning devices are examples for CPU modules that can be available via J2. Digital and analog outputs of I/O modules are possible as well.
These signals are routed through the backplane to a Rear Transition or Rear I/O board. The Rear I/O board looks like a shortened Eurocard and also has a front panel with additional connectors.
Thus, it is possible to feed all cables into the back. The CPU and peripheral components can easily be accessed from the front. Another important aspect is the protection of cables. The Rear I/O cabling for example is inside the switch cabinet where it is protected against mechanical wear and tear.
The third aspect seems far fetched but is
far from unimportant: In case of service the module does not need to be touched
preventing COM1 and COM2 from being mixed-up and avoiding other errors.
Searching for an error which had its source in two mixed-up channels is
certainly a common experience.
The
staged (multi-length) pins in the CompactPCI connector cause some connections to
be made before others when inserting a card. The reverse occurs when a card is
removed. This, in principle, allows CompactPCI products to be hot swapped. This
is a complex issue, however, and significant efforts are underway by a number of
PICMG member companies to develop a quality solution. There are some significant
obstacles to be overcome. First, special circuitry must be developed so that a
board can be inserted and removed from a live, operating PCI bus. Second, DC
power to boards being hot swapped must generally be ramped up and down to avoid
"glitching" the system's DC bus. Thirdly, applications software and
operating systems must be developed that recognize when a board is removed and
another inserted. This will be required to re-initialize complex I/O chips like
graphics adaptors or network interfaces. Despite these obstacles, however, hot
swap is a very desirable feature and a great deal of energy is being devoted to
developing viable techniques.
6.
What does 3U mean? What
does 4HP mean?
The modules height and width as well as all their accessories are standardized in a 19-inch frame for use in industrial applications worldwide. The resulting advantages for larger systems or complex installations are clear. On the outside, a subrack of normal width measures 482.6 mm (= 19”). However, absolute dimensions are rare in daily use.
The internal spacing is divided in
Horizontal Pitch (HP). A 19” subrack has 84 HP. Due to the height of the
electronic components (on the module), 4HP is defined as the minimum width. Up
to 21 modules therefore fit into an 84 HP subrack. If modules consist of more
than one board, e.g. CPUs, the module grows in steps of 4 HP. The same applies
to I/O modules requiring more space for front panel connectors. In this case a
module may need 8 or 12 HP.
The subrack’s height is specified by Units (U) in the 19” system. Subracks for simple Eurocards usually have 3 U (dual Eurocards have 6 U). Further accessories like a fan unit with 1 U or space for cable conduits or similar can also require any other design.
If subracks do not require the entire width, systems with 3 U / 32 HP or 4 U / 24 HP or any other combination are possible. However, the spacing of 1 HP / U is maintained to avoid proprietary designs.
Height
x depth: Eurocard 100 x 160 mm, dual Eurocard 233.35 x 160 mm.
|
|
Dimension
for front panel (internal dimension of subrack) |
Typical
external dimensions of subrack |
|
1U
|
41,33 mm (
1.63”) |
44,45 mm ( 1 ¾”) |
|
3U |
130,00
mm (
5.12”) |
133,00
mm ( 5 ¼“) |
|
6U |
260,00
mm (10.24”) |
263,00
mm (10.35“) |
|
1HP |
5,08 mm (
0.2”) |
|
|
4HP |
20,30 mm (
0.8“) |
|
|
42HP |
213,15
mm ( 8.4“) |
269,45
mm (10.6“) |
|
84HP |
426,40
mm (16.8“) |
482,60
mm (19“) |
|
84HP
without mounting brackets |
|
441,00
mm (17.4“) |
7.
What are the
advantages of 3U as compared to 6U?
First of all, the disadvantages of 3 U systems: Due to a smaller board the layout is more difficult and requires more consideration and effort in order to place the desired functions. In addition, the halved front panel never provides enough space for external connections. Why do we still try?
From a mechanical point of view the 3U size is more resistant, better fixed in the subrack and therefore less susceptible to shocks and vibrations. This alone would be an argument to justify the higher developmental effort.
With 3U boards the module’s type and number can be more easily adapted to the application.
Beyond this there is another effect: The available mounting space is rather short in height than in width. Of course this statement has to be considered empirically. Please reflect on your last three projects: Did you have any space problems? If yes, in height or width or in both dimensions?
8.
Can
I integrate CompactPCI boards from different manufacturers in one system?
Yes,
you can. The technically advanced state of the CompactPCI system should leave no
room for surprises. Though having said that, difficulties might arise in case of
driver and software support for (third party) modules. Problems in this area can
sometimes lead to changing the third party supplier.
9.
How
do I integrate a normal PCI board / ISA board into a CompactPCI system?
A
PCI module like it is found in a normal PC (with PICMG 1.x standard) needs to be
both mechanically and electrically integrated in a 19” subrack. This is
possible only with great efforts, requires space, and should only be done in
case of emergency. However, the problem of direct plug-in is not solved. Such an
adapter is available in the open market.
In addition, an ISA module needs to be converted from the ISA bus to the PCI bus (ISA/ PCI bridging). This can only be realized for certain functions and needs to be considered from case to case.
Other
bus systems
PCI Express concerns an advanced variant of the existing standards PCI and PCI-X. PCI Express routes data via one or more serial wire pairs while PCI and PCI-X route data and addresses with 33 or 66 MHz pulse frequency via a parallel 32 or 64 Bit bus system. This is considered as a serial bus on chip level. A “pair of transmit wires” (Tx) and a “pair of receive wires” (Rx) are called Express conduit. Every PCI Express conduit is able to transmit and receive with 2.5 GBit/s at the same time. In order to transmit one Byte 10 bits are needed due to the overhead. Thus, the data transmission rate is calculated as follows:
2.5
GBit/s x 2 (Rx/Tx) = 0.5 GByte/s
10 Bit
A PCI Express bus may consist of 1 to 32
conduits and can therefore transmit data up to 16 GByte/s.
PCI Express offers more
performance with fewer pins – and therefore less cost.
2.
What is AdvancedTCA /
CompactTCA?
The telecommunication sector has very high requirements on system availability (99.999% uptime). To support this, PICMG started a dedicated solution called Advanced Telecom Computing Architecture, or AdvancedTCA.
With this, the available board size of 6 U was not sufficient to fulfill the desired functions. The AdvancedTCA standard defines an 8 U board size. The module’s width is 6 HP. In addition, the tremendous requirements of data transmission on those modules led to data transmission rates up to 1 Terabit/s with AdvancedTCA. Special serial connectors (Dual Star, Full Mesh) provide for this. To support the processing power needed, each module can sue 200 Watts.
The mechanical density requires certain precautions and cooling from an ATCA system. Thus, up to 2.8 kW waste heat can dissipate in a subrack with 14 modules.
In the meantime, a “small” module variant has been developed: The CompactTCA with modules of 6 HP. Special CompactPCI modules can be inserted in AdvancedTCA systems via an adapter.
3.
PICMG 3.0
PICMG
3.0 is the base specification of Advanced TCA (see here).
It defines Power
Distribution, Mechanical Elements, System management, Connector zones and
types, Fabric topologies, thermal management guidelines, and Regulatory
Guidelines.
The other specifications in this series PICMG 3.x define different
serial communication networks, like Ethernet and Fibre
Channel, InfiniBand, StarFabric, PCI-Express and Advanced Switching, and
RapidIO..
Advanced
Mezzanine Card Specification for high speed modules.
AMC.0 is the core spec. Target interfaces include PCI Express, Advanced
Switching, Serial RapidIO, and Gigabit Ethernet.
Includes system management and hot swap support
