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Definition of PCI
PCI: Peripheral Component Interconnect
PCI is a local bus standard for connecting peripherals to a personal computer.
Within a computer, the bus is the transmission path on which signals and data
transfers occur between the CPU, system memory, and attached devices such as a
network card, sound card, or CD-ROM drive.
| Conventional PCI |
Plug-and-Play Functionality
Standard PCI is 32 bit and operates at 33 MHz
32-Bit throughput 133 MB/sec
PCI 2.1 introduced
Universal PCI cards supporting both 3.3V and 5V
64 Bit slots and 66 MHz capability
32-Bit throughput @ 66 MHz: 266 MB/sec
64-Bit throughput @ 66 MHz: 532 MB/sec
PCI 2.3 system no longer supports 5V-only adapters
3.3V and Universal PCI products are still fully supported |
The PCI Local Bus (usually shortened to PCI), or Conventional PCI, is a
computer bus for attaching hardware devices in a computer. The PCI
bus is common in PCs, where it displaced ISA Local Bus as the standard
expansion bus. Despite the availability of faster interfaces such as
PCI-X and PCI Express, conventional PCI remains a very common interface.
The PCI specification covers the physical size of the bus (including
wire spacing), electrical characteristics, bus timing, and protocols.
Typical PCI cards used in PCs include: network cards, sound cards,
modems, extra ports such as USB or serial, TV tuner cards and disk
controllers. Historically video cards were typically PCI devices, but
growing bandwidth requirements soon outgrew the capabilities of PCI.
replaced by AGP or PCI Express cards.
Many PCI devices traditionally provided on expansion cards are now
integrated onto the motherboard itself. |
| PCI Express |
High-speed point-to-point architecture that is
essentially a serialized, packetized version of PCI
General purpose serial I/O bus for chip-to-chip communication, USB
2.0 / IEEE 1349b interconnects, and high-end graphics. A viable AGP
replacement.
Bandwidth 4 Gigabit/second full duplex per lane
Up to 32 separate lanes
128 Gigabit/second
Software-compatible with PCI device driver model
Expected to coexist with and not displace technologies like PCI-X in
the foreseeable future |
PCI Express (Peripheral Component Interconnect Express),
officially abbreviated as PCIe, is a computer expansion card standard designed
to replace the older PCI, PCI-X, and AGP standards. Introduced by Intel in 2004,
PCIe (or PCI-E, as it is commonly called) is the latest standard for expansion
cards that is available on mainstream personal computers
PCI Express is used in consumer, server, and industrial applications, both as a
motherboard-level interconnect (to link motherboard-mounted peripherals) and as
an expansion card interface for add-in boards. A key difference between PCIe and
earlier PC buses is a topology based on point-to-point serial links, rather than
a shared parallel bus architecture.
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Tech note |
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Since
PCI Express is a serial based technology, data can be sent over
the bus in two directions at once. Normal PCI is Parallel, and
as such all data goes in one direction.
Each 1x lane in PCI Express can
transmit in both directions at once. PCI Express
bandwidth is not shared the same way as in PCI, so there is less
congestion on the bus.
The
"x" in an "x16" connection stands for "by." PCIe connections are
scalable by one, by two, by four, and so on.
When
the computer starts up, PCIe determines which devices are
plugged into the motherboard. It then identifies the links
between the devices, creating a map of where traffic will go and
negotiating the width of each link. |
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| PCI-X |
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PCI-X (PCI eXtended) is a computer bus and expansion card standard that
enhanced the PCI Local Bus for higher bandwidth demanded by servers. It
is a double-wide version of PCI, running at up to four times the clock
speed, but is otherwise similar in electrical implementation and uses
the same protocol. It has itself been replaced in modern designs by the
similar-sounding PCI Express, which features a very different logical
design, most notably being a "narrow but fast" serial connection instead
of a "wide but slow" parallel connection. |
PCI-X 1.0
Based on existing PCI architecture
64-Bit slots with support for 3.3V and Universal PCI
No support for 5V-only boards
Fully backwards-compatible
Conventional 33/66 MHz PCI adapters can be used in PCI-X slots
PCI-X adapters can be used in conventional PCI slots
Provides two speed grades: 66 MHz and 133 MHz
The slowest board dictates the maximum speed on a particular bus
Targeted at high-end data networking and storage network applications
PCI-X 2.0
Based on PCI-X 1.0
Still fully backwards-compatible
Introduces ECC (Error Correction Codes) mechanism to improve robustness and
data integrity
Provides two additional speed grades
PCI-X 266: 266 MHz (2.13 GB/sec)
PCI-X 533: 533 MHz (4.26 GB/sec)
Bandwidth sufficient to support new breed
of cutting-edge technologies
10 Gigabit Ethernet / Fiber Channel
4X / 12X InfiniBand
PCI-X 3.0
Became available in 2004
Backwards-compatible with PCI-X 1.0 / 2.0
PCI-X 1066 provides 1066 MHz data rate with 8.5 GB/sec bandwidth
PCI-X Speed Limitations
PCI-X supports point-to-point and multi-drop loads
Highest speed grades are supported exclusively with point-to-point loads
PCI-X 133
PCI-X 266
PCI-X 533
PCI-X 1066
Two PCI-X 133 loads operate at 100 MHz
Four loads operate at a maximum of 66 MHz
OEMs can build connector-less systems with multiple loads utilizing high
speed grades
Some technical information provided by Digi.com
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