> The combination with a mask of B'0111' limits addressing to 24 bits. > It does work in AMODE 31 and 24, but not on a 360.
In this case it doesn't matter, because IBM uses bits 0-7 of that word in the DCB for flags, so 24 bits is all that's left. > A colleague, working for MIPS/SGI had to steadfastly refuse requests from > software >developers not to validate upper bits of 64-bit addresses, prohibiting their >use for flags. Not my monkeys, not my circus, but how do you spell "Hell, no"? -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of Paul Gilmartin [0000042bfe9c879d-dmarc-requ...@listserv.ua.edu] Sent: Sunday, February 19, 2023 12:52 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: BSAM Read 31 bit mode On Sun, 19 Feb 2023 17:14:14 +0000, Seymour J Metz wrote: >> THe ICM clears bits 0-7 of the (SYNAD?) address. > >It's the XR that clears bits 0-7, not the ICM. > The combination with a mask of B'0111' limits addressing to 24 bits. It does work in AMODE 31 and 24, but not on a 360. >That's not what OPTABLE is for; many macros test the globals set by SYSSTATE, >which is why it's there. > Thanks. >> 31-bit is underreaching. Should be 64. > >Agreed, unless technology advances much more rapidly than I expect. But 24-bit >was also underreaching when S/360 came out, given what was already on the >market. > A colleague, working for MIPS/SGI had to steadfastly refuse requests from software developers not to validate upper bits of 64-bit addresses, prohibiting their use for flags. Assembler is the wrong language for upward compatibility. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
