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10. 5 B o a rd C o n t ro l E x te n s i o n s
10.5.1 SPI Boot Flash Selection—uEFI BIOS Failover Control
The uEFI BIOS code is stored in two different SPI boot flash devices designated as the standard SPI boot
flash and the recovery SPI boot flash.
By default, the uEFI BIOS code stored in the standard SPI boot flash is executed first. If this fails, the
uEFI BIOS code in the recovery SPI boot flash is then executed.
During boot-up, the uEFI BIOS reports its operational status to the MMC within a given time. If the sta-
tus is "failed" or not reported within the given time, the MMC selects the recovery SPI boot flash, resets
the board's processor, and waits for the status report from the uEFI BIOS again.
In the event the recovery boot operation fails, the MMC reports it, but takes no further action of its
own.
When a boot operation fails, a "Boot Error - Invalid boot sector" event is asserted for the related sensor:
»
"FWH0 Boot Err" sensor indicates the standard SPI boot flash has failed
»
"FWH1 Boot Err" sensor indicates the recovery SPI boot flash has failed
10.5.2 uEFI BIOS Boot Order Selection
Normally, the uEFI BIOS will apply the boot order which was selected in the uEFI BIOS menu "uEFI Boot/
Boot Option Priorities". But there is another alternative boot order, which is stored in the MMC's non-
volatile memory. This boot order can be set and read by IPMI OEM commands. At payload start the MMC
writes this boot order into a register where the uEFI BIOS can read it. If this MMC's boot order has a
non-zero value, the uEFI BIOS will use it instead of its own boot order.
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