On Mon, 27 Mar 2017 18:10:35 -0400 Charles Mills <charl...@mcn.org> wrote:
:>The fact that the hardware guys and gals made the hardware capable of execution above the bar means IBM is giving this some thought. (The thought may be "Heck, no!" <g>) Well, they never supported code execution from a dataspace ...... :>-----Original Message----- :>From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Paul Gilmartin :>Sent: Monday, March 27, 2017 5:00 PM :>To: IBM-MAIN@LISTSERV.UA.EDU :>Subject: Re: 64 bit execution above the bar :>On Mon, 27 Mar 2017 15:19:31 -0500, Dave Anderson wrote: :>>What is IBM's strategy for migrating code execution to be above the bar? Has IBM released any documents detailing the next steps, or is this confidential? :>It has been discussed here for a while. You could disable interrupts, branch to code above the bar, and branch back later. (I suppose the Old PSW was unconditionally scrunched.) More recently, interrupts above the bar are tolerated, but no system services can be called from above the bar. :>>Currently data areas above the bar are widely used but program execution above the bar is not currently supported. Other posts have suggested that Cobol will soon support 64 bit execution but not only for modules loaded below the bar and that 64 bit Cobol is unlikely to be widely used as it is not compatible with 31 bit Cobol and has performance issues. :>Performance issues have been mentioned here. Are those because of: :>o I-fetch bandwidth? :>o Address calculation/translation overhead? :>o Computation overhead? :>o Some combination? :>I'd guess that instructions with 64-bit operands are slower than instructions with shorter operands, even in AMODE 24/31. :>Is AMODE 31 slower than AMODE 24? (Or even the opposite?) :>>Does anybody know if IBM plans to run system modules above the bar? I would be interested in hearing any comments/insights on this topic? :>Not I. How close is LPA to encountering a Virtual Address Storage Constraint? -- Binyamin Dissen <bdis...@dissensoftware.com> http://www.dissensoftware.com Director, Dissen Software, Bar & Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. I very rarely bother responding to challenge/response systems, especially those from irresponsible companies. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
