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PCI Express� Architecture
Frequently Asked Questions
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Q1: What is PCI Express� architecture?
A1: PCI Express architecture is an industry standard high-performance,
general-purpose serial I/O interconnect designed for use in enterprise,
desktop, mobile, communications and embedded platforms. It has many
state-of-the-art attributes, including:
- PCI compatibility using the established PCI software programming
models, thus facilitating a smooth transition to new hardware while
allowing software to evolve to take advantage of PCI Express features
- A cost-effective, low-pin count interface offering maximum bandwidth
per pin, reducing cost and design complexity and enabling smaller form
factors
- Scalable bandwidth of 16 Gigabytes per second at its initial signaling
rate of 2.5GHz with much higher transfer rates in the future using higher
frequency signaling technologies
- Support for multiple interconnect widths via 1, 2, 4, 8, 12, 16 and 32
lane configurations aggregated to match application bandwidth needs
- Support for new and innovative, hot-plug/hot-swap add-in card and
module devices
- Unique, advanced features such as Power Management, Quality of Service
and other native functions not available in other I/O architectures
Q2: What prompted the creation of PCI Express architecture?
A2: The interconnect demands of emerging compute and communications
platforms exceed the capabilities of traditional parallel busses such as
PCI. Innovations such as 10GHz and higher CPU speeds, faster memories,
high-end graphics gigabit networking and storage interfaces, and
high-performance consumer devices have driven the need for a system
interconnect with much greater bandwidth scalability and lower cost of
implementation. PCI Express architecture uniquely meets these varying market
segments requirements.
Q3: How does PCI-SIG� ensure product interoperability?
A3: PCI-SIG holds regular Compliance Workshops in various locations around
the world to satisfy the needs of its members. These workshops are intended
for members to demonstrate their product's interoperability with those of
other PCI-SIG members. Member products that successfully demonstrate
interoperability at a workshop are listed on the PCI-SIG Integrators List.
Member products that conform to the PCI Express architecture may use the PCI
Express logo (registered trademark of PCI-SIG) subject to the PCI-SIG
Trademark and Logo Usage Guidelines.
Q4: What and how many PCI Express architecture specifications are
there?
A4: The PCI Express architecture suite of specifications can be described as
follows:
- PCI Express Base Specification: the core specification for the
multi-layered PCI Express architecture. It is currently at revision
1.1.
- PCI Express Card Electromechanical Specification: the ATX-based form
factors. It is currently at revision 1.1.
- PCI Express Mini Card Electromechanical Specification: the BTO/CTO
mobile platform form factor. It is currently at revision 1.1.
- PCI Express to PCI/PCI-X� Bridge Specification: the bridging
architecture to enable PCI Express components to function with legacy PCI
devices. It is currently at revision 1.0.
- PCI Express x16 Graphics 150W-ATX: the considerations for power and
thermal issues in the next generation of platforms with leading-edge
graphics and multimedia applications to deliver higher performance
capabilities. It is currently at version 1.0.
- PCI Express ExpressModule�: a hot-pluggable modular form factor defined
for servers and workstations. It is currently at revision 1.0.
PCI Express Form Factors
Q5: What is the PCI Express x16 Graphics 150W-ATX 1.0
Specification?
A5: PCI Express x16 Graphics 150W-ATX 1.0 is a supplementary specification
to the PCI Express architecture specification specifically for delivery for
higher performance capabilities for the next generation of platforms with
leading-edge graphics and multimedia applications. The specification
considers power and thermal issues in these platforms and provides a
solution space for designers of these systems.
Q6: What is PCI Express ExpressModule?
A6: The ExpressModule� Specification is a new PCI Express modular form
factor defined for Servers & Workstations. Its ease-of-use packaging and
integrated features provide benefits to many customers and system
integrators (OEM, IHV, VAR and End-users). The ExpressModule enables and
promotes fundamental improvements in the way Servers & Workstations are
built and serviced.
Q7: How does ExpressModule improve the way Servers and Workstations
are built and serviced?
A7: The ExpressModule form factor provides Servers and Workstations with a
modular I/O adapter that is closed chassis hot-pluggable. The design of
ExpressModule frees the I/O adapter from direct connection to the system
board, thus allowing greater flexibility in system design. Server I/O
Modules can be placed in the front or back of system, vertical or
horizontal, or above system I/O board. The Server I/O Modules flow-through
cooling model increases system venting while providing adapter developers a
know airflow scheme, thus improving reliability for both adapters and
systems. The standard management features promotes remote service while the
modular enclosure enables customer service and upgrades.
Q8: What is the PCI Express Wireless Form Factor (WFF)?
A8: WFF is a new form factor being developed within PCI-SIG by member
companies focused on the unique requirements associated with integrating
existing and new wireless technology into a wide range of usage models, e.g.
portable notebook computers.
Q9: What is the PCI Express External Cable specification?
A9: The PCI Express External Cabling specification is being developed to
address multiple market segment cable requirements to extend PCI Express
protocol and functionality across arbitrary distances and packaging that
cannot be met using existing backplane trace connectivity.
Architectures Related to PCI Express Technology
Q10: What is ExpressCard* technology?
A10: ExpressCard technology is the name of a new standard introduced by
PCMCIA in spring 2003. The ExpressCard standard promises to deliver thinner,
faster and lighter modular expansion to desktop and notebook computer users.
Consumers will be able to add hardware capabilities such as memory, wired
and wireless communications and security features by simply inserting a
module into their systems. All ExpressCard slots will accommodate modules
designed to use either Universal Serial Bus (USB) 2.0, or the emerging PCI
Express standards. Over time ExpressCard technology is expected to become
the preferred solution for hot-pluggable internal I/O expansion for desktop
and mobile computers.
Q11: Who developed the ExpressCard standard?
A11: The ExpressCard standard was created by a broad coalition of PCMCIA
member companies, including Dell, Hewlett Packard, IBM, Intel, Lexar Media,
Microsoft, SCM Microsystems and Texas Instruments. PCMCIA developed the new
standard with assistance from the USB Implementers Forum (USB-IF) and
PCI-SIG. PCMCIA is a non-profit trade association founded in 1989 to
establish technical standards for PC Card technology and to promote
interchangeability among computer systems.
Q12: How can PCI Express developers build components that can be
integrated into ExpressCard products?
A12: First, developers must use silicon that has passed the PCI-SIG
compliance program. PCI Express components that successfully pass the
PCI-SIG compliance tests may be useable in an ExpressCard module if they
allow for a module design which meets the additional requirements (e.g.,
power management, power and thermal) detailed in the ExpressCard standard.
System and module developers must also pass the PCMCIA ExpressCard
compliance program to qualify to use the ExpressCard logo.
Q13: What is the compliance program for ExpressCard
products?
A13: PCMCIA has developed a ExpressCard compliance program which is similar
to, and draws upon the programs offered by PCI-SIG and USB-IF. Products
which pass these tests will be licensed to display the ExpressCard name and
logo on their products.
The ExpressCard compliance program s a two-step process including a self
administered checklist and an interoperability test. The interoperability
events will be held in conjunction with PCI-SIG or USB-IF Compliance
Workshops. In the future we will provide developers the alternative option
of using external test houses.
Q14: Where can interested parties get more information?
A14: The specification and support collaterals has been published by the
PCMCIA and is available at www.expresscard.org. PCI-SIG and
USB-IF (www.usb.org) are also publishing
relevant information for developers.
*All third party trademarks are the property of their respective
owners.
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