On 18 March 2014 12:00, Paul Gilmartin <paulgboul...@aim.com> wrote: > How did the 67 deal with legacy code's use of the sign bit to terminate > parameter lists?
I doubt that much legacy code ran on such a machine in 32-bit mode. There would surely be other reasons to run such code only in 24-bit mode - not least the common use of the entire high byte of an address to hold flags and such. > Did it also have a 31-bit mode? But I suppose most such code was written for > 24-bit addressing. It did not have 31-bit mode. PSW bit 4 was the 24/32 switch when in Extended PSW mode, which in turn was controlled by a Control Register bit. It's interesting that USASCII mode (bit 12, which became the BC/EC bit in virtual storage S/370s) was supported in both PSW modes. But I never actually saw one, let alone worked on it, so I'm just interpreting the Functional Characteristics. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
