PCI 2.2 allows for 66 MHz signalling (requires 3.3 volt signalling) (peak transfer rate of 533 MB/s)
PCI-X changes
the protocol slightly and increases the data rate to 133 MHz (peak transfer
rate of 1066 MB/s). See more below
PCI-X 2.0 specifies a 266 MHz
rate (peak transfer rate of 2133 MB/s) and also 533 MHz rate,
expands
the configuration space to 4096 bytes,
adds a 16-bit bus variant and allows
for 1.5 volt signalling
Compact PCI uses Eurocard-sized modules plugged into a PCI backplane.
Mini PCI is a new form factor of PCI 2.2 for use mainly inside laptops Mini PCI products (this site)
PCI Express, or PCIe, (formerly Arapaho
or 3GIO, 3rd generation IO), a new interface using PCI programming concepts,
with
a much faster serial physical-layer protocol and different connectors.
PCI
Express is expected to replace the PCI (and PCI-derived AGP) buses.
The physical-layer
consists not of a bus, but of a network of serial interconnects (because synchronization
of parallel connections is hindered by timing skew) much like twisted pair ethernet.
A single hub with many pins on the mainboard is used, allowing all kinds of
switching and parallelism.
PCI Express is intended to be used as a local interconnect
only. As it is based on the existing PCI system, cards and systems can be converted
to PCI Express by changing the physical layer only – existing systems could
be adapted to PCI Express without any change in software. The higher speeds on
PCI Express allow it to replace almost all existing internal buses, including
AGP and PCI, and Intel envisions a single PCI Express controller talking to all
external devices, as opposed to the northbridge/southbridge solution in current
machines.
Cardbus is a PCMCIA (PC Card) form factor for 32-bit, 33 MHz PCI
ExpressCard is a hardware standard replacing CardBus. ExpressCard
Serial ports ExpressCard
Firewire & USB ports
The host device supports both PCI Express and
USB 2.0 connectivity through the ExpressCard slot,
and each card uses
whichever the designer feels most appropriate to the task.
The cards are hot-pluggable.
ExpressCard
supports two form factors, ExpressCard/34 (34 mm wide) and ExpressCard/54 (54
mm wide, in an L-shape) — the connector is the same width (34 mm) on both.
Standard cards are 75 mm long (10.6 mm shorter than CardBus) and 5 mm thick, but
may be thicker on sections that extend outside the standard form factor —
for antennas, sockets, etc.
More ExpressCard Info: www.expresscard.org
PC/104-Plus is an industrial bus that utilizes the PCI signal lines with different connectors.
ATCA or AdvancedTCA: Advanced Telecommunications Computing Architecture, is a next-generation bus for the telecommunications industry
A "Universal" PCI board is compatible with both 5V and 3.3V signaling environments.
Universal PCI
boards detect the voltage provided on a dedicated PCI connector pin (VIO), and
configure themselves automatically for the correct PCI bus logic levels.
Some confusion exists among users regarding the designation of a PCI board or
slot as "3.3V," "5V" or "universal,"
all of
these references should pertain to the PCI signalling levels (i.e.: logic
levels), and not to a power requirement.
Up to Revision 2.3 of the PCI
specification all PCI-compliant bus configurations must provide all four power
rails,
i.e.: +5V, +3.3V and ±12V.
Possible
PCI environments
32-bit / 3.3 V / 33 MHz 64-bit / 3.3 V /
33 MHz
32-bit / 3.3 V / 66 MHz 64-bit / 3.3 V / 66 MHz
66 MHz is only possible with 3.3 V signalling, 3.3 V boards or universal boards
32-bit / 5 V / 33 MHz 64-bit / 5 V / 33 MHz 5
V boards are not allowed to be connected to a 66MHz interface
66
MHz versus 33 MHz
The 66 MHz PCI bus is a compatible superset
of PCI defined to operate up to a maximum clock speed of 66 MHz.
Differences
between 33 MHz PCI and 66 MHz are minimal.
Both share the same protocol, signal
definitions and connector layout.
33 MHz devices may be used on 66MHz PCI
buses, 66 MHz devices may be used on 33 MHz PCI buses, and in both cases the bus
operation will be 33 MHz.
The most important changes from 33 MHz to 66 MHz
are: ..
66 MHz PCI bus uses the 3.3 V signaling environment ..
One static
signal is added on 66 MHz to identify it as a 66 MHz device ..
Timing parameters
have been scaled to 66 MHz.
PCI-X: A compatible extension of the existing PCI Bus, the 64-bit PCI-X architecture runs at speeds up to 133 MHz, providing burst transfer rates above 1gigabyte per second. This critical I/O bandwidth is needed for industry standard servers running enterprise applications such as Gigabit Ethernet, Fibre Channel, Ultra3 SCSI and Cluster Interconnects.
In addition to performance improvements, PCI-X also increases the fault isolation of the PCI bus by helping the operating system work more effectively with adapters to better manage error conditions.
PCI-X ensures investment protection because it offers backward compatibility with existing PCI based systems and a stable and complementary technology roadmap for future I/O standard system architectures. PCI-X technology will be available in Compaq server and workstation products beginning in the second half of the year 2000.
PCI-X offers both added performance and flexibility minimizing
the trade-off between PCI slots and bus speed.
For example, based on preliminary
simulation testing,
a 66 MHz four-slot implementation of PCI-X shows more
than a twenty-five percent increase in I/O performance over a conventional
PCI bus running at its maximum configuration (64-bit 66 MHz).
It is also
possible to use multiple PCI-X buses at different speeds, providing a combination
of ultra-high performance and maximum slot capacity.
The PCI-X Specification is an open industry standard and available from the PCI Special Interest Group (SIG) as an addendum to the PCI Local Bus 2.2 Specification.