[LinuxBIOS] RE: E7501 raminit changes
Steven J. Magnani
steve at digidescorp.com
Thu Jun 23 22:33:45 CEST 2005
>Does anyone know if de-asserting A20M# is enough to cause A20 to behave
>normally? On our board, after we force A20M# high, the system continues
to
>behave as if A20 is always zero. We're using an embedded board, so
there is no
>keyboard controller in the mix - I/O port 0x92 is enough to toggle
A20M#.
A note for the record. It appears to be a feature of the Xeon that a
change in A20M# doesn't take effect until after the processor steps
forward at least one instruction. So if you use an emulator to stop the
processor and toggle A20M#, you won't see any change in memory behavior
until you step through the next instruction.
Doh!
Steve
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