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Technical Reference Guide
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition - September1997
4-45
4.7.2 PASSWORD PROTECTION
When enabled, the user is prompted to enter the power-on password during POST. If an
incorrect entry is made, the system halts and does not boot. The Power-On password is stored in
eight bytes at configuration memory locations 37h-3Fh. These locations are physically located
within the 87307. At the time a new password is written into 37h-3Fh, the password is also
written into Black Box* logic. The Black Box logic is used for power-on password protection
support instead of the port 92 sequence used on other systems. The Black Box logic prevents
inadvertent or unauthorized access to the password bytes of the 87307 by monitoring I/O ports
70/71h for access to the 37h-3Fh CMOS range and inhibiting the AEN signal to the 87307 if
such access is detected. Slot 1 of the Black Box logic can be written to at runtime, allowing the
user to change the power on password without cycling power and going through the F10 method.
The Black Box password cannot be read.
The power-on password function can be disabled by setting DIP SW1 position 1 to on (closed).
The administrator password is stored in eight bytes at configuration memory locations 77h-7Fh.
If the administrator password function is enabled, the user is prompted to enter the password
before running F10-Setup or before booting from a ROMPAQ diskette. If an incorrect entry is
made, the system boots although system administration functions are inhibited. The
administrator password is also stored in the Black Box* logic. Black Box logic acting as the
sentry for the administrator password by preventing inadvertent or unauthorized writing to the
Flash ROM.
*
Black Box logic is Compaq-proprietary and controlled exclusively through firmware in BIOS ROM.