On Thu, 9 Dec 2010 11:13:42 -0500, Watkins, Douglas wrote: >So, Tom, is it a common misconception that only addresses from >1_00000000 and up are above the bar? I thought that was the original >reason for the "bar" designation, "thickness" being an intentional >attribute.
It is a misconception. I can't say how common it is. An address is above the bar if it can only addressed with the processor running in 64-bit mode. That is, bits 31 and 32 of the PSW are both 1. AFAIK, the reason for calling it a bar is to distinguish it from the line that is at 16M. Addresses above 16M cannot be referenced when running in 24-bit mode. They could have designated the old "line" as the "16M line" and designated the bar as the "2G line". That would have required that everyone change the way that they think about "above the line". -- Tom Marchant
