External Interrupt has always been a grab bag, even on S/360. S/370 added more events that I wouldn't describe as external. The list is pretty long these days.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of Tom Brennan <t...@tombrennansoftware.com> Sent: Saturday, October 19, 2019 7:24 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Best way for a task to give up the CPU and let other tasks run? Interesting, thanks! So it generates an external interrupt. I always thought that one was only for the external interrupt "key", but this page indicates CPU timer and some kind of CP-to-CP communication too: https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconc_interrupts.htm Ok... now back to my weekend work, like changing the oil in my truck. On 10/19/2019 3:54 PM, Charles Mills wrote: > Check out "CPU Timer" in the Principles of Operation. > > Charles > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On > Behalf Of Charles Mills > Sent: Saturday, October 19, 2019 12:47 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Best way for a task to give up the CPU and let other tasks run? > > Thanks! > > I suppose some encryption algorithm for which there was no hardware assist > available might be a more practical real-world scenario. > >> Is there something in the dispatcher that is on a timer that ends up saying >> this task has gotten enough CPU and it's time to move to the next TCB? > > In my way imperfect understanding, yes. I believe there is a hardware feature > now wherein MVS can say "give me an interrupt when this CPU has run for nnn > CPU microseconds" or something similar. > > If not, then most operating systems have a concept of the time slice: we will > let set a hardware timer for nnn real-time microseconds and when the timer > goes off, re-evaluate our scheduling algorithm. > > Charles > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On > Behalf Of Tom Brennan > Sent: Saturday, October 19, 2019 12:37 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Best way for a task to give up the CPU and let other tasks run? > > Great descriptions! I was thinking of the PI calculation myself because > that's a case where you're doing real work, but the loop could be coded > with no I/O and no SVC calls (which would give up control). Now here's > a case I thought about in the past: Assuming I'm running such a PI > calculation (non-supervisor, interrupts enabled), what is it that > eventually interrupts my running code? Of course there are previous I/O > completions from other tasks or CP's, but imagine (maybe on a > specialized system?) there's nothing much else going on. Is there > something in the dispatcher that is on a timer that ends up saying this > task has gotten enough CPU and it's time to move to the next TCB? > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
