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FH8065401488912

Volume 2—Platform Controller Unit (PCU)—C2000 Product Family

Root Complex Register Block (RCRB)

Intel

®

Atom™ Processor C2000 Product Family for Microserver

Datasheet, Vol. 2 of 3

September 2014

372

Order Number: 330061-002US

16.5

Root Complex Register Block (RCRB)

The PCU contains the Root Complex Register Block (RCRB). This block is a 32-bit

register that is memory-mapped I/O, with the base address in the iLB Configuration

registers. The register is named the General Control and Status (GCS) and contains the

BIOS configuration and status needed for the BIOS/EFI boot.

16.5.1

Boot BIOS Straps (BBS)

The BIOS/EFI is booted from either the PCU SPI interface or the iLB LPC interface. The

choice of SPI or LPC is configured by the 2-bit Boot BIOS Straps (BBS) field in the

General Control and Status (GCS) register (address 0x0000 in the RCRB). The

configurations of the BBS are indicated in

. During power-up, these bits are

affected by the external strap pin FLEX_CLK_SE0.

Note:

The BIOS/EFI boot from the LPC interface is not available when Secure Boot is enabled.

Note:

Writes to GCS.BBS are unsuccessful if the GCS.BILD bit has been set which means that

the GCS.BBS setting has been locked-down by the software.

Table 16-6. BBS Configurations

Boot BIOS Straps (GCS.BBS)

Description

00

Boot from LPC

11

Boot from SPI

01 or 10

Reserved