Interesting evolution of 24 - 31 - 64 bit addressing : - 16MB is a real euclidian "line" i.e. zero thickness. - 2GB "line" has a thickness of 4KB - Now the bar is 2GB wide.
As for the need of a "guaranteed bad address", is it something similar to a NULL pointer in C ? If I recall correctly, C implemets NULL pointers as X'0' which off course would run into issues with PSA access here. By the way how was this need satisfied in 24 bit days ? Or was it that the need hadn't arisen yet ? Just curious Mohammad On Thu, 8 Nov 2007 17:48:05 -0500, Jim Mulder <[EMAIL PROTECTED]> wrote: >IBM Mainframe Discussion List <IBM-MAIN@BAMA.UA.EDU> wrote on 11/08/2007 >12:24:52 PM: > >> On Thu, 8 Nov 2007 08:43:03 -0800 Edward Jaffe ><[EMAIL PROTECTED]> >> wrote: >> >> :>There is also a one-page "hole" at 7FFFF000. (Another handy >> :>implementation choice made by your friendly-neighborhood z/OS >developers!) >> >> Interesting. Is that hole documented? > > I don't know if it is documented, but it has been that way since the >beginning of MVS/XA, and isn't going to change. > >> >> Is there any 24 bit virtual address which is never assigned a slot? >> > > No, there is no such 24 bit virtual address. With only 4,096 >pages that are 24-bit addressable, I guess we didn't want to >dedicate one of them for that purpose. > >Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
