This is certainly not my area of expertise, but here's how I understand it after discussion here with folks who know more about it.
Back in the old pre-CMOS days, external interrupts like I/O were handled by one or more of the same CPs that calculated dividend interest or life expectancy or rocket velocity. We had some control over how many CPs were drafted into interrupt handling, such as parameters in IEAOPTxx that could include or exclude CPs according to how busy they got. With the introduction of CMOS (967x), the CEC as delivered provided physically distinct Service Assist Processors that relieved the mainline CPs from having to perform these tasks. The tuning recommendation changed at that time to allow the system full control over use of the SAPs by coding CPENABLE=(0,0) . I don't know how many SAPs various models contain, but RMF indicates that our z900s have four. . . JO.Skip Robinson Southern California Edison Company SHARE MVS Program Co-Manager 626-302-7535 Office 323-715-0595 Mobile [EMAIL PROTECTED] IBM Mainframe Discussion List <[email protected]> wrote on 03/27/2006 04:00:00 PM: > >If that is so, then is it still true that one engine is often dedicated > to dealing with interrupts? > > At least one. > You can have up to three (pre-z9), depending on how many CP's are active. > I was told three; I have never had more than two. > (I have never had more than 10 CP's, either). > > SAP - Service Assist Processor > Originally called: IOP > Originally stood for I/O Processor. > Changed to Integrated Offload Processor (ES/9000 Series), changed to > SAP with the 9672. > > Truly, the first specialty engine. > Introduced on the 308x, IIRC. > > - > -teD ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
