Datasheet

Intel® S5000 Server Board Family Datasheet Functional Architecture

Revision 1.3

Intel order number D38960-006

2.4 I/O Sub-system

The I/O sub-system consists of several components:

 PCI sub-system

 Serial ATA (SATA) support

 Serial-attached SCSI (SAS)

 RAID support

 Parallel ATA (PATA) support

 Video controller

 Network interface controller (NIC)

 USB 2.0 support

 Super I/O support

This section describes the function of each I/O interface and how they operate.

2.4.1 PCI Sub-system

2.4.2 Scan Order

The BIOS assigns PCI bus numbers in a depth-first hierarchy, in accordance with the PCI Local

Bus Specification, Revision 2.2. The bus number is incremented when BIOS locates a bridge

device that is not part of the chipset. Scanning continues on the secondary side of the bridge

until all subordinate buses are assigned numbers. PCI bus number assignments may vary from

boot to boot with varying presence of PCI devices with PCI-PCI bridges. If a device with a

bridge with a single bus behind it is inserted into a PCI bus, all subsequent PCI bus numbers

below the current bus are increased by one.

The bus assignments occur once, early in the BIOS boot process, and never change during the

pre-boot phase.

2.4.3 Resource Assignment

The BIOS resource manager assigns the PIC-mode interrupt for the devices that are accessed

by the legacy code. The BIOS will ensure the PCI BAR registers and the command register for

all devices are correctly set up to match the behavior of the legacy BIOS after booting to a

legacy operating system. Any legacy code cannot make any assumption about the scan order of

devices or the order in which resources are allocated to them.

In legacy mode, the BIOS supports the INT 1Ah PCI BIOS interface calls.

2.4.4 Automatic IRQ Assignment

The BIOS automatically assigns IRQs to devices in the system for legacy compatibility. No

method is provided to manually configure the IRQs for devices.