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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.

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.

Hello

May be you can try port 0x92

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

K.J. wrote: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.

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

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.

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

K.J.