Chapter 16: System switches, user switches, BIOS update and LEDs
System switches
Various system function options are selected with Switch 500.
The “S” switch selects whether the card boots from user defined parameters
(defined in the Setup Programs chapter), or the BIOS defaults. Setting this switch
Off allows the user to return to factory programmed defaults.
The “V” switch enables or disables the on-card video, allowing an external video
card, or the serial console to be used.
The “X” switch is reserved for future use.
The “U” switch is user defined and can be used for program control.
Table 16
−
1 System
configuration switches, Switch 500
Switch 500 – System Configuration
Label Description
Position
S
System parameters option switch:
1
On = enable User Setup options*
Off = enable BIOS Setup default
V Video
switch:
2
On = enable on-card video*
Off = disable on-card video
X
reserved for future use
3
U
User switch, default On*
4
* = default
System switch
The system switch is position 1. When this switch is On the system boots using the
parameters stored in Setup. When this switch is Off the system boots using the
factory defaults for all parameters in Setup. Note that if you must set the system
switch Off to recover your system, the user-defined parameters in Setup will not be
changed unless you enter Setup, make the changes, and exit saving changes.
Video switch
The video switch is position 2. When this switch is On the on-card video is enabled.
To use a serial console, or an extension-card video only without using the onboard
video controller (such as a PC/104), set this switch Off.
User switch
The user switch is position 4 and is associated with GP13. The INT17 functions
provide an easy method to implement software routines according to whether or
not a switch is On. Refer to the INT17 calls to read user switch on page 91.
90
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