Rick Fochtman wrote:
------------------------<snip>----------------------
Correct. For an amode24 program, the entire universe ends at address
x'00FFFFFF'; the "next step" wraps back to x'00000000'. So for an
amode24 program, there is nothing "above the line" or "above the bar"
because for it, there is neither a "line" nor a "bar".
That's also my understanding.
So, again, why 24-bit programs could be a reason for 2-4G hole ?
-------------------------<unsnip>--------------------------
Because bit 0 is the switch between 24-bit mode and 31-bit mode, and
as such cannot participate in an address.
This is simply not true!!
The two AMODE bits (BA & EA) are in the PSW, not in address words. And,
they don't conflict in any way with the 64-bit Instruction address in
the PSW or any of the bits used for addressing in a 64-bit general
purpose register. See the PSW format below. And, please read my prior
post(s) in this thread for the reason why the purely optional, yet
highly valuable, 2G-4G "dead" zone was implemented for z/OS.
+---------------------------------------------------------------+
& & & & & & &I&E& & & & & & & & Prog & &E&
&0&R&0&0&0&T&O&X& Key &0&M&W&P&A S&C C& Mask &0 0 0 0 0 0 0&A&
+---------------------------------------------------------------+
0 5 8 12 16 18 20 24 31
+---------------------------------------------------------------+
&B& |
&A&0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|
+---------------------------------------------------------------+
32 63
+---------------------------------------------------------------+
& Instruction Address &
+---------------------------------------------------------------+
64 95
+---------------------------------------------------------------+
& Instruction Address (Continued) &
+---------------------------------------------------------------+
96 127
--
Edward E Jaffe
Phoenix Software International, Inc
5200 W Century Blvd, Suite 800
Los Angeles, CA 90045
310-338-0400 x318
[EMAIL PROTECTED]
http://www.phoenixsoftware.com/
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