On Wed, 6 Jul 2011 13:34:28 +0000, Bill Fairchild <bi...@mainstar.com> wrote:
>A few days ago I composed and sent a post in which I believed that the bar was the 2GB line because I had just seen a comment statement inside the IARV64 macro that stated that as a fact. Today I reviewed an IBM SHARE presentation in which the word "bar" was attached to a very wide arrow pointing at the middle of the 2GB area in between virtual addresses 2GB and 4GB. So I must conclude that the technical term "bar" officially means whatever IBM wants it to mean today, where the meaning of "today" changes from day to day. This situation is very much like that of another controversial term which once meant the U.S. Steel Corporation (inter alia). > I'm not sure which presentation you looked at, Bill, but Elpida's presentation (mentioned yesterday in this thread) clearly shows the bar as being the 2G line (chart on page 48). And to me, nothing else makes much sense today. Yes, originally we had a 2GiB dead space between 2**31 and (2**32)-1, but we no longer have that. Instead, we revised it that so that a 32GiB area starting at 2**31 was reserved for use by Java. And then we further revised that so there's an additional 256GiB above that reserved for system usage. "Above the bar" is perhaps still a useful term, but the real question is whether one is dealing with 31- or 64-bit addresses, and one might speak in those terms instead. The exact location of the storage should have little or no relevance to most programs and programmers, but I suppose one might argue that for normal programs, the "bar" now has a thickness of 288 GiB rather than the old thickness of 2GiB. (I would not make that argument, however; I would say the bar has no thickness.) -- Walt ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
