Is it possible to enable the A20 without a keyboard?

[K.J.]

Is it possible to enable the A20 without a keyboard? I think that there must be a way, as there are x86 devices that have no keyboard, but can run Windows.

K.J.

[DynatOS]

I think all the those "devices" require the existance of the 8042, keyboard usage or not, so there should be no problem in Stuart's code.

[gedeon]

Hello

May be you can try port 0x92

[The Legend]

There is a faster way to enable A20, but it can be disabled in some BIOSes by switching off the Fast A20 Gate-Option.

[Tim]

Is it possible to enable the A20 without a keyboard?

Yes. Any AT-compatible system (i.e. a PC) will have a keyboard controller even if there's nothing plugged into it: the keyboard controller is a separate chip which interfaces to the keyboard itself, and contains other circuitry for things like rebooting the machine, gating A20 and talking to a PS/2 mouse.

[f2]

in al,0x92
or al,0x02
out 0x92,al

[DynatOS]

Check HERE, you will see some problems with the 0x92 i/o port, plus you will find that it is mandatory to have the 8042 or something that will "emulate" the A20 charactersitics of it.

[K.J.]

Thanks for all the info, I always thought that the 8042 was in the keyboard.

K.J.