BIOS Initialization ESB2 BMC Core TPS
Revision 1.0
Intel order number E18291-001
144
invokes the ACPI OSHP method to transfer control of the HPC from the firmware to the
operating system.
14.3.4.1 PCI Hot-plug Controller Initialization in Pre-Boot Phase
The Hot-plug Controllers (HPC) come up in an un-initialized state after a power-off or reset. As
a result, the hot-plug slots come up in an un-powered state. The BIOS initializes the hot-plug
controllers during the boot process. Hot-plug controller initialization involves applying power to
the hot-plug slots and detecting any error conditions during link initialization.
The IDT PCI Express* Expander devices provide Hot-plug Controller support compliant with the
PCI Express Base Specification, Revision 1.1. This support allows the following actions to occur
without powering down the system:
PCI card removal
PCI card replacement
PCI card addition
14.3.4.2 PCI Hot-plug Resource Padding in Pre-Boot Phase
The BIOS over-allocates resources to PCI slots during boot process. This is called resource
padding. The over-allocation is done at the PCI-PCI bridge level. Over-allocation of resources
allows a limited number of add-in cards to be hot-plugged into a PCI bus without disturbing the
allocation to the rest of the busses.
By default the BIOS reserves the following set of resources for each hot-pluggable slot
regardless of the presence of a card in the slot:
One bus number
4KB I/O
64 MB non-prefetch memory below 4 GB
64 MB prefetch memory below 4 GB
14.3.4.2.1 Direct Effect of Resource Padding
The direct effect of the resource padding is as follows:
The total memory allocated by the BIOS to the PCI subsystem increases.
The main memory available to the operating system in the 0 to 4 GB range decreases
according to the lower bounds of the memory addresses allocated to PCI.
The PCI Express Base Specification, Revision 1.1 defines a standard usage model for PCI Hot-
plug. The usage model specifies several elements including the state of the indicator LEDs’
interlocking switches. The server provides these hardware elements and the BIOS supports
them in accordance with this specification.
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