Back in OS/360 IBM shipped code that was reentrant but not refreshable. I don't know whether they shipped code that was refreshable but not read only, although I wouldn't be surprised.
Paging existed prior to S/360. In fact, one of the disappointments in the S/360 announcement was that IBM didn't initially include it. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List [[email protected]] on behalf of Charles Mills [[email protected]] Sent: Monday, August 16, 2021 9:03 PM To: [email protected] Subject: Re: RENT binder option A program might have a counter in the CSECT that the logic incremented as an aid to debugging. That would S0C4 if storage protected, but the program logic would be fine if the CSECT were refreshed. Granted, something of a stretch. At the time, paging did not exist. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Paul Gilmartin Sent: Monday, August 16, 2021 3:25 PM To: [email protected] Subject: Re: RENT binder option On Mon, 16 Aug 2021 21:38:23 +0000, Seymour J Metz wrote: >IBM originally used REFR in support of the mahine check handler; if you got a >parity error in certain refreshable modules then MCH would read in a fresh >copy. REFR did not reuire that the module be read-only, just that refreshing >it would not cause errors. > That's true of successful operation does not depend on that modified content. I find it hard to envision such a design. > ... On modern processors, when there is a good copy of the page on DASD, > discarding a page frame with an unrecoverable memory failure is a better > solution for the same reliability concern. > IOW, the MCH meed only mark the frame as invalid and let paging handle it? (Almost immediately when the failing instruction is retried.) ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
