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8086, segment address offset FFFF: FFFF more than 1 MB?

Time:04-15

FFFF: FFFF
This writing is in conformity with the rules, but it's more than 1 MB, what will happen?

CodePudding user response:

This, see the A20 line state, if it is closed, address wrap, and final result still only 20, beyond the shed when does not exist, if opened, will further expand access to space, to form the so-called HMA area, more than regular 1 m (64-10 h k) in space, the DOS can be configured to use the interval to load some drive, to make more of the routine space available,
More specific detail accurate, can with the keyword search and see,

CodePudding user response:

HMA, UMB... For many years didn't hear the ~