Actually, BAL/BALR came first. BAS/BASR, in different forms, were on the later 360/20 and 360/67.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of Randy Hudson <i...@panix.com> Sent: Tuesday, February 11, 2020 11:53 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Backward compat--how far? In article <52550040-57eb-4a48-9627-e5c6444fe...@googlegroups.com>, <foll...@gmail.com> wrote: > I've got a copy of "IBM Operating System/360 Assembler Language" copyright > December 1964. Pretty sure all the opcodes listed in Appendix B (Machine > Instruction Mnemonic Codes) are still supported by the hardware (I haven't > checked 'em all). There are some 360/20-only codes that might not work. I recall a BAS and BASR, op codes 0D and 4D, that were the predecessors of the BAL and BALR instruction. Since the registers on the 360/20 were only 16 bits, they only saved the low-order 16 bits of the PSW for a return address (BAL/BALR store 32 bits, the bottom 24 of which are the return address). ---------------------------------------------------------------------- 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
