On Mon, 3 Jun 2013 10:08:19 -0500, Tom Marchant wrote:
>
>Why do you continue to refer to the area between 2GB and 4GB as 
>"Within the bar"?   While it is true that some early presentations 
>depicted the bar as having a "thickness" of 2 GB, AFAIK, it was never 
>documented that way in any IBM manual.  Rather, the manuals 
>describe the area above 2 GB as "above the bar".
> 
The construct is such a convenient abbreviation that I see little
reason to discontinue its historic use.


>In any case, the area that has been reserved for Java is (IIRC) 
>from 2GB to 32 GB, well beyond 4 GB.
> 
I stand corrected.  ITYM 2GiB to 32GiB.

>>in order to
>>employ 32-bit addressing without triggering further below the bar VSCR.
>
It's an interpreter.  An interpreter can use whatever representation of
addresses it chooses.  Rexx, for example, represents addresses as hexadecimal
display values of variable length.  But, yes, now that you've reminded me,
32GiB requires larger addresses than 32 bits.  (Probably.  If an interpreter
were make its smallest unit of addressable storage 8 bytes, it could still
address 32GiB with 32 bit addresses.  I doubt that Java is implemented in
that fashion.)

-- gil

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