Nothing like that is required. My understanding is that when the PSW is stored it is compressed down to an ESA/390 PSW format (check bit 12) and expanded when it is reloaded. There is no point at which an 8-byte PSW is "active" in any sense.
>There are indeed many programs that inspect the 8-byte PSW, but not that many >that manipulate the address portion. And those that do typically do something >"reasonable" with the address, such as a) replacing it altogether with another >address or b) adjusting the address by 2, 4 or 6 bytes (or the ILC) to cause an >instruction to be re-executed or skipped. z/OS can probably compare the 8-byte >PSW at re-dispatch time against a copy saved at interrupt time and, if it has >changed, guess right 99% of the time as to what should be done to the 16-byte >PSW to effect the intended change(s) just by following just a few simple rules. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
