Specifications

PC BIOS
10-12 PP 41x/03x
10.6 The Recovery BIOS
In the unlikely event that the board’s BIOS ROM contents becomes corrupted and it is not possible
to perform the normal BIOS update procedure, the board provides a minimal Recovery BIOS that
will allow the board to boot from a specially prepared floppy disk and restore a known-good BIOS
image.
The Recovery BIOS is located in a special sector in the BIOS ROM that is protected from
accidental erasure by hardware means. When a BIOS update is performed, the Recovery BIOS
does not get updated.
When power is applied to the board, or when the board is reset, the CPU starts to execute the
Recovery BIOS. From here a checksum test is performed on the first 64Kbytes of the main BIOS to
ensure that it is intact. When the checksum is validated, control passes to the main BIOS and the
board boots normally. If the checksum test fails, the BIOS recovery process is invoked
automatically.
The BIOS recovery process can also be forced using the Boot Type Switch, see Figure 10-3.
Figure 10-3 Boot Type Switch
The recovery BIOS will indicate its progress via a serial terminal connected to COM1 or COM2, as
determined by the Console Port Switch (see Figure 6-2). VGA output is not supported.
The recovery BIOS requires a specially prepared disk image: a suitable recovery disk image can
be obtained from Concurrent Technologies, if required.