Pci Express Configuration Switch; Bios Select And Mode Configuration Switch - ADLINK Technology COM Express Express-BL User Manual

4.6.2.

PCI Express Configuration Switch

The PCI Express Configuration Switch allows you to configure the PCI Express x16 lanes from the CPU as 1 PCIe x16, 2 PCIe x8, or
1 PCIe x8 + 2 PCIe x4.
Mode
1x PCIe x16 (default)
2x PCIe x8
1x PCIe x8 + 2x PCIe x4
Reserved
4.6.3.

BIOS Select and Mode Configuration Switch

The module has two BIOS chips and BIOS operation can be configured to "PICMG" and dual-BIOS "Failsafe" modes using the BIOS Select
and Mode Configuration Switch, Pin 2.
Setting the module to PICMG mode will configure the BIOS chips on the module as SPI0 and SPI1. In PICMG mode, a BIOS chip cannot be
placed in the SPI0 slot on the carrier.
In dual-BIOS Failsafe mode, both BIOS chips on the module are configured as SPI1. Only one of the two is connected to the SPI bus at any
given time. In case of failure of the primary SPI1 BIOS, the system will reboot and switch to the secondary SPI1 BIOS on the module. In
Failsafe mode, the SPI0 BIOS socket on the carrier can be populated.
In either mode, BIOS Select and Mode Configuration Switch, Pin 1 is used to select whether to boot from SPI0 or SPI1.
Mode
Boot from SPI0 (default)
Boot from SPI1
Set BIOS to PICMG mode
Set BIOS to Failsafe BIOS mode (default)
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Pin 1 Pin 2
Off Off
On Off
On On
Off On
Pin 1 Pin 2
On —
Off —
— On
— Off