Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!gem.mps.ohio-state.edu!ginosko!uunet!sco!seanf From: seanf@sco.COM (Sean Fagan) Newsgroups: comp.arch Subject: Re: Instruction (dis)continuation Message-ID: <3267@scolex.sco.COM> Date: 3 Sep 89 21:45:39 GMT References: <1989Aug24.215104.156@mentor.com> <231@ssp1.idca.tds.philips.nl> <2345@oakhill.UUCP> <204@bbxeng.UUCP> <5990@pt.cs.cmu.edu> <205@bbxeng.UUCP> <265@gp.govt.nz> <45180@bbn.COM> Reply-To: seanf@sco.COM (Sean Fagan) Organization: The Santa Cruz Operation, Inc. Lines: 25 In article <45180@bbn.COM> dswartz@BBN.COM (Dan Swartzendruber) writes: >Although it is possible to construct a >theoretical scenario where an instruction restart CPU could get into an >infinite page-fault loop, I will respectfully suggest that if your system >only has 6 free pages of memory, the effective result (as far as getting >any useful work done is concerned) will be pretty much the same! Somebody else also gave the example: movw $300, $100 (obviously a VAX 8-)). Dan is, I think, following up to the comment that, if you're tight on free memory, swapping the page with $100 could cause the page with $300 to be swapped out (and vice-versa), which would cause real problems with instruction restart. Now, my point: how about shared memory? (SysV-type shared memory, not multi-processor-type shared memory.) With instruction restart, the value in $300 could have changed, while, with instruction continuation, it doesn't matter. How do various OS's and hardwares handle it? -- Sean Eric Fagan | "Time has little to do with infinity and jelly donuts." seanf@sco.UUCP | -- Thomas Magnum (Tom Selleck), _Magnum, P.I._ (408) 458-1422 | Any opinions expressed are my own, not my employers'.