Dell 2650 manual Expansion Cards, Replacing the Expansion-Card Cage, PCI Bus Scan Order

Replacing the Expansion-Card Cage

CAUTION: Before you perform this procedure, read the safety instructions in your System Information document.

CAUTION: See "Protecting Against Electrostatic Discharge" in the safety instructions in your System Information document.

NOTICE: To avoid damage to the system, keep the bottom of the expansion-card cage parallel to the system board, while lowering the cage into the chassis.

1.With the expansion-card cage lever in the upright position, carefully lower the cage into the chassis until it is aligned with the tabs on the chassis side wall (see Figure 4-11).

2.Rotate the expansion-card cage lever down until the handle is flush with the top of the cage, and the cage is secured in the chassis (see Figure 4-11).

3.Reconnect all expansion-card cables.

4.Replace the cover (see "Replacing the Cover").

Expansion Cards

The system includes three expansion slots. The expansion cards are installed on the system's riser board (see Figure 5-4 to identify the expansion slots).

Expansion Card Installation Guidelines

Use the following guidelines when installing expansion cards:

•You can install expansion cards of different operating speeds on the same bus; however, the bus will operate at the slowest operating speed of the cards on that bus. For example, if one card on the bus has an operating speed of 33 MHz and the other card has an operating speed of 66 MHz, the bus will only operate at 33 MHz.

•When installing a boot controller expansion card, such as a RAID or SCSI controller card, install the boot controller card in expansion slot 1. This position allows your operating system to properly use the boot controller card. For more information, see "PCI Bus Scan Order."

To identify expansion slots and PCI buses, see Figure 5-4. Table 4-1 lists the PCI bus and operating speed for each expansion-card slot.

Table 4-1. Expansion Slot Speeds

Slot	Bus	Operating Speed
1	1	Up to 100 MHz
2	1	•	Slot 1 is not empty — up to 100 MHz
		•	Slot 1 is empty — up to 133 MHz
3	2	Up to 133 MHz

NOTE: If you are using expansion cards of different operating speeds, you should install the fastest card in slot 3 and the slowest card in slot 1.

PCI Bus Scan Order

The system's BIOS scans and numbers PCI buses and devices during startup. Expansion slots are scanned according to the host bus ordering, not by the slot numbers. See Table 4-2 for the order in which the expansion slots and embedded PCI devices are scanned. Figure 5-4 provides a diagram of buses and expansion slots.

Certain operating systems do not allow the PCI bus number of the system's boot controller to change after the operating system loads. Installing an expansion card with its own PCI bridge chip in an expansion slot earlier in the PCI bus scan order than the boot controller can cause the renumbering of the boot controller PCI bus number. To allow your operating system to properly use the boot controller expansion card, install the boot controller card, such as a RAID or SCSI controller card, in expansion slot 1.

An additional factor affects the assignment of PCI bus numbers: an expansion card may have its own PCI bridge chip which requires the assignment of a bus number for the card as well as one for the bridge. A particular expansion card may have two PCI bridge chips which would result in three sequential PCI bus numbers all assigned in the same expansion slot.

If you install expansion cards, you may have some difficulty in directly determining the bus number of a controller on a particular expansion card. However, the PCI bus scan order listed in Table 4-2 can help determine the relative numbering of PCI buses within the expansion slots. For example, a PCI controller residing in expansion slot 3 will never have a lower bus number than one in slot 2 because slot 2 precedes slot 3 in the scan order.

Table 4-2. PCI Bus Scan Order

Order	Device or Slot
1	Video
2	Embedded remote access components
3	Expansion slot 1
4	Expansion slot 2
5	Expansion slot 3
6	Integrated NIC 1