[email protected] (Tom Marchant) writes: > Bi-modal? You mean like MVS/XA? Or do you mean that you > could run it in ESA mode? From the 1.6 announcement: > > "z/OS V1.6 must execute in a z/Architecture (64-bit) mode."
above/below line was originally introduced with >16mbyte real storage for 3033 ... 64mbyte option or "26bit" real addressing. all instructions were still 24bit (16mbyte) ... but a hack to the pagetables allowed pages to be located in real storage above 16mbytes. 24bit virtual addresses were run thru address translation ... and the pagetable hack could result in 14bit real page number. original 370 (4k page option) was 12bit virtual page number into pagetables with 12bit real page number out. page table entry was 16bits; 12bit real page number, 2 defined bits, and 2 undefined bits. the 3033 64mbyte hack ... retasked the undefined bits as 2bit prefix to the standard 12bit real page number ... for 14bit real (4kbyte) page number (up to 64mbytes real). 370 IDAL was also hacked to support 26bit i/o address (enabling direct page in/out above 16mbyte line). however ... all sorts of stuff still had to be in the first 16mbytes real storage (introducing above/below line issues). misc. recent posts mentioning >16mbyte support originally for 3033: http://www.garlic.com/~lynn/2010.html#84 locate mode, was Happy DEC-10 Day http://www.garlic.com/~lynn/2010g.html#11 Mainframe Executive article on the death of tape http://www.garlic.com/~lynn/2010g.html#36 16:32 far pointers in OpenWatcom C/C++ http://www.garlic.com/~lynn/2010g.html#55 Mainframe Executive article on the death of tape for moving stuff between above & below the 16mbyte line ... there was originally plan to do page out and then page back in (running page move thru i/o system courtesy of IDAL). I provided a little example code where pagetable entries were fiddled for above & below the line addresses ... with a MVCL for move across the line (lot more efficient than doing it thru the page i/o system). some old email providing the MVCL hack (for crossing 16mbyte line, also mentions that 3081 & XA schedule was slipping so additional storage was extending life/revenue for 3033): http://www.garlic.com/~lynn/2006t.html#email800121 in this post http://www.garlic.com/~lynn/2006t.html#15 more than 16mbyte support for 370 -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- 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
