Chapter 3
23
Gate A20 Option
This BIOS feature is used to determine the method by which Gate A20 is controlled.
The
Normal
option forces the chipset to use the slow keyboard controller to do the
switching. The
Fast
option, on the other hand, allows the chipset to use its own 0x92
port for faster switching. No candy for guessing which is the recommended setting!
Please note this feature is only important for operating systems that switch a lot
between real mode and protected mode. These operating systems include 16-bit
operating systems like MS-DOS and 16-bit/32-bit hybrid operating systems like
Microsoft Windows 98.
This feature has no effect if the operating system only runs in real mode (
no operating
system currently in use does that, as far as I know!
) or if the operating system
operates entirely in protected mode (
i.e. Microsoft Windows XP
). This is because if
A20 mode switching is not required, then it does not matter at all if the switching was
done by the slow keyboard controller or the faster 0x92 port.
With all that said and done, the recommended setting for this BIOS feature is still
Fast
, even with operating systems that don't do much mode switching. Although using
the 0x92 port to control Gate A20 has been known to cause spontaneous reboots in
certain, very rare instances, there is really no reason why you should keep using the
slow keyboard controller to turn A20 or off.
Typematic Rate Setting
The feature allows you to control the keystroke repeat feature.
If
enabled
, you can manually adjust the two following:
l
Typematic Rate
l
Typematic Rate Delay
If
disabled
, the foregoing features will be disabled and greened out. The keyboard
controller will then use the default Typematic Rate & Typematic Rate Delay.
Typematic Rate (Chars/Sec)
You can use this feature only when the
Typematic Rate Setting
is
enabled
. The
feature allows users to determine at what rate the keyboard will repeat the keystroke
when you press it continuously. The higher the typematic rate is, the faster the
keyboard will repeat the keystroke.
Typematic Rate Delay (Msec)
This BIOS setting will only work if the
Typematic Rate Setting
feature has been
enabled.
This feature determines how long, in
milliseconds
(
thousandths of a second
), the
keyboard controller will wait before it starts repeating the keystroke that you have
pressed continuously. The longer the delay, the longer the keyboard controller will
