shmuel+ibm-m...@patriot.net (Shmuel Metz , Seymour J.) writes: > Certainly. If I recall correctly, MDF was implemented in what Amdahl > called macrocode, not by dedicated hardware. So what triggered the > redispatch at the end of a time slice if not an external interrupt?
the guys doing MDF use to come to baybunch and pump me for information ... I had done time-slice dispatching since my undergraduate days in the 60s and had been involved in design and implementation of ECPS for the 138/148 ... there have numerous issues over the years with implementations trying to get around use of timer-based considerations ... hoping that other events would provide sufficient control not having to resort to the additional overhead ... this has periodically resulted in monumental gafs when the various other failed to occur in the anticipated ways. the other issue was that the MDF implementation for Amdahl was significantly simpler because of the macrocode use. 3090 had to respond with pr/sm ... but that was a significantly more complex undertaking because there wasn't any equivalent facility and they had to fallback to horizontal microcode. there was also issue in the early 1980s when somebody having gotten an award for changes to mvs/xa, contacted me about whether similar changes could be made to vm. I commented that I had not done it any other way since my work as undergraduate in the 60s ... and in fact had arguments with VS2/SVS (precursor to MVS) in the early 70s about they shouldn't be doing it the wrong way. past posts mentioning part of the effort for ECPS http://www.garlic.com/~lynn/94.html#21 past posts mentioning dispatching/scheduling http://www.garlic.com/~lynn/subtopic.html#fairshare misc past posts mentioning macrocode: http://www.garlic.com/~lynn/2002p.html#44 Linux paging http://www.garlic.com/~lynn/2002p.html#48 Linux paging http://www.garlic.com/~lynn/2003.html#9 Mainframe System Programmer/Administrator market demand? http://www.garlic.com/~lynn/2003.html#56 Wild hardware idea http://www.garlic.com/~lynn/2005d.html#59 Misuse of word "microcode" http://www.garlic.com/~lynn/2005d.html#60 Misuse of word "microcode" http://www.garlic.com/~lynn/2005h.html#24 Description of a new old-fashioned programming language http://www.garlic.com/~lynn/2005p.html#14 Multicores http://www.garlic.com/~lynn/2005p.html#29 Documentation for the New Instructions for the z9 Processor http://www.garlic.com/~lynn/2005u.html#40 POWER6 on zSeries? http://www.garlic.com/~lynn/2005u.html#43 POWER6 on zSeries? http://www.garlic.com/~lynn/2005u.html#48 POWER6 on zSeries? http://www.garlic.com/~lynn/2006b.html#38 blast from the past ... macrocode http://www.garlic.com/~lynn/2006c.html#9 Mainframe Jobs Going Away http://www.garlic.com/~lynn/2006j.html#32 Code density and performance? http://www.garlic.com/~lynn/2006j.html#35 Code density and performance? http://www.garlic.com/~lynn/2006m.html#39 Using different storage key's http://www.garlic.com/~lynn/2006p.html#42 old hypervisor email http://www.garlic.com/~lynn/2006u.html#33 Assembler question http://www.garlic.com/~lynn/2006u.html#34 Assembler question http://www.garlic.com/~lynn/2006v.html#20 Ranking of non-IBM mainframe builders? http://www.garlic.com/~lynn/2007b.html#1 How many 36-bit Unix ports in the old days? http://www.garlic.com/~lynn/2007d.html#3 Has anyone ever used self-modifying microcode? Would it even be useful? http://www.garlic.com/~lynn/2007d.html#9 Has anyone ever used self-modifying microcode? Would it even be useful? http://www.garlic.com/~lynn/2007j.html#84 VLIW pre-history http://www.garlic.com/~lynn/2007k.html#74 Non-Standard Mainframe Language? http://www.garlic.com/~lynn/2007n.html#96 some questions about System z PR/SM http://www.garlic.com/~lynn/2008c.html#32 New Opcodes http://www.garlic.com/~lynn/2008c.html#33 New Opcodes http://www.garlic.com/~lynn/2008c.html#42 New Opcodes http://www.garlic.com/~lynn/2008j.html#26 Op codes removed from z/10 http://www.garlic.com/~lynn/2008r.html#27 CPU time/instruction table http://www.garlic.com/~lynn/2010m.html#74 z millicode: where does it reside? http://www.garlic.com/~lynn/2011c.html#93 Irrational desire to author fundamental interfaces -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
