IBM Personal System/2 65 SX User Manual

remains set so that POST can read this bit. If the bit is set
to 0, POST assumes the system was just powered on. If
the bit is set to 1, POST assumes a switch from the
protected mode to the real mode has taken place.
When bit 0 is used to reset the system microprocessor to
the real mode, use the following procedure:
1. Disable all maskable and nonmaskable interrupts.
2. Reset the system microprocessor by writing bit 0 to 1.
3. Issue a Halt instruction to the system microprocessor.
If this procedure is not followed, the results will be
unpredictable.
Note: Whenever possible, BIOS or ABIOS shouid be used
as an interface to reset the system microprocessor
to the real mode.
Power-On Password
Eight bytes of RT/CMOS RAM are reserved for the power-on
password and its check character. The eight bytes are initialized to
hex 00. The microprocessor can access these bytes only during
POST. After the completion of a POST, if a power-on password is
installed, the password bytes are locked and cannot be accessed by a
program. The power-on password can be from one to seven
characters.
During power-on password installation, the password (1 to 7 keyboard
scan codes), is stored in the security space.
Installing the password is a function of a program on the Reference
Diskette. The power-on password does not appear on the screen
when you install, change, or remove it. Once you instali the
power-on password, it can be changed only during POST.
The system unit cover can be physically locked to prevent access to
the speaker/password security connector.
The Model 65 SX also has a keyboard password. For more
information, see the Hardware Interface Technical Reference
keyboard and auxiliary-device controller information.
Model 65 System Board — October 1990 3-25

IBM Personal System/2 65 SX Specifications

General

Brand	IBM
Model	Personal System/2 65 SX
Category	Desktop
Language	English