[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
>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

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.



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