EMC QLogic Installation Guide download pdf (Page 23)

Installing the HBA

Installation and Configuration

Figure 3 HBA edge connecters

PCI-X (or PCI Extended) slots increase the speed that data travels

over the bus. PCI-X slots appear identical to a 64-Bit PCI slot keyed

for 3.3v. (Refer to number 3 in Figure 2 on page 20 and Figure 3.)

PCI-X slots are backwards compatible with 3.3v PCI HBAs and

universal HBAs. Inserting standard PCI HBAs into PCI-X slots will

lower the bus speed, however, as they cannot take advantage of the

improved performance.

PCI-X 2.0 is the next generation of PCI-X buses. PCI-X 2.0 increases

the bus speed providing more performance for HBAs. PCI-X 2.0 slots

also appear identical to a 64-bit PCI slot keyed for 3.3v. (Refer to

number 3 in Figure 2 on page 20 and Figure 3.) PCI-X 2.0 is also fully

backward-compatible with 3.3v PCI and PCI-X.

PCI Express (sometimes noted as PCIe) is a new bus type that uses

the existing PCI model, but implements it in a faster, serial protocol.

Because of the serial way it transmits data, the PCI Express bus slot

can be different sizesdepending onthe throughput it supports. PCI

Express slot speeds are expressed in "lanes" and are normally shown

as x1, x4, x8, and x16. Each type of slot are different lengths (Figure 4

on page 22) and HBA edge connecters will also have varying lengths

depending on how many lanes they require for throughput. Because

of how PCI Express slots are keyed, an x1 HBA can be inserted in all 4

slot types as the HBA will negotiate with the slot to determine the

highest mutually supported number of lanes. However, an HBA

requiring x16 lanes will not fit into a smaller slot.

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EMC QLogic Installation Guide Page 23