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15654Re: [midatlanticretro] Re: the party...

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  • Brian Schenkenberger, VAXman-
    Dec 14, 2009
      Ray Sills <raysills@...> writes:

      >Somewhere in the bowels of MARCH's collection of "stuff" is an "Icepik"
      >or two. That was one of those gadgets that would let you freeze an
      >operating program, and then make a RAM dump on to a disk. On reloading
      >-that- disk, you jumped right back into an operating program.

      Interesting. Can you elaborate some on this "Icepik"'s implementation?

      Such a tool would be very difficult to use on today's processors, even
      if you DID manage freeze and dump, and restore from said dump. States
      of CPU caches, instruction lookahead, virtual memory translation tables
      and multi-proccessor and interprocessor interrupts and interlocks would
      cause no end to the headaches of trying to resurrect a system from some
      snapshot. Perhaps such a thing is doable on a small system with a mini-
      scule memory space but it's incredibly complex in today's larger systems
      with huge virtual memory address spaces. Hell even 4GB is a lot of mem-
      ory to read in. If there's an external processor available (control or
      monitor or console) it's easier. There's simply too much trampling of
      the system's memory if trying to use the system CPU to fixup all that's
      read in. Such a feature was implemented in VMS V6. but then abandoned
      due to the complexity as newer features were added -- external storage
      controllers for one. The feature was called "snapshot" and "fastboot"
      for anyone interested in googling it.

      VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)COM

      "Well my son, life is like a beanstalk, isn't it?"
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