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AlphaServer ES47/ES80 and GS1280 systems offer three types of I/O bus standards for adapters and controllers.
1.
PCI-X
— Peripheral Component Interconnect Extended is a computer bus interface standard for connecting a
microprocessor and attached devices. PCI-X doubles the speed and amount of data exchanged between the computer
processor and peripherals from the predecessor PCI bus. PCI-X is backwards-compatible, meaning that users can, for
example, install a PCI-X card in a standard PCI slot but expect a decrease in speed to 66 MHz or 33 MHz. Users can
also use both PCI and PCI-X cards on the same PCI-X bus, but the bus will run at the speed of the slowest card. PCI-X
is more fault tolerant than PCI. For example, PCI-X is able to reinitialize a faulty card or take it offline before computer
failure occurs.
2.
PCI
— Peripheral Component Interconnect is a computer bus interface standard for connecting a microprocessor and
attached devices.
3.
AGP 4 —
Accelerated Graphics Port (AGP) is an interface specification that enables 3-D graphics to display quickly. It is
especially useful in conjunction with three-dimensional (3D) video, and sophisticated scientific and engineering graphics
programs. AGP runs at several times the bus speed of conventional Peripheral Component Interconnect (PCI). Because
of this, the data transfer rate using AGP is significantly greater than with PCI video cards. The AGP 4X mode provides
high performance levels with a peak bandwidth of 1066 MB/s. AGP 4X mode is a superset to the 1X and 2X modes;
thus, all components supporting AGP 4X must also support 1X and 2X modes.
The following table presents the matrix of maximum, theoretical I/O throughput for the different standards. Actual I/O
throughput will be less than calculated because of protocol overhead and contention for bus capacity.
Calculated Maximum Throughput
32-bit data path 64-bit data path
PCI, 33 MHz
0.133 GB/s 0.267 GB/s
PCI or PCI-X, 66 MHz
0.267 GB/s 0.533 GB/s
PCI-X, 100 MHz
N/A
0.8 GB/s
PCI-X, 133 MHz
N/A
1.067 GB/s
Calculated Maximum Throughput
1X 2X 4X
AGP
0.133 GB/s 0.267 GB/s 1.067 GB/s
Overall System Capacities for I/O Adapters and Controllers
QuickSpecs
HP AlphaServer GS1280 Systems
ES/GS Common Options
DA - 11921 Worldwide — Version 24 — July 23, 2007
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