Fwd: Does the KA630 have a TB?

[Andrew Ball <asbatwrk%gmail.com@localhost>]

Hello Paul,

   M> I have not.  I grabbed a copy of simh some time ago, but I never
    > got around to convincing it to build.

 ASB> It built and runs on my amd64 machine.  It's not fast and of
    > course even when the simulated VAX isn't busy the host machine
    > is kept busy emulating the idle VAX.  It's one of the few things
    > I do that make me want a faster desktop computer.

  PK> SIMH can handle idling and does so very well, provided it knows
    > the idling scheme used.  On some machines, like the PDP-11, the
    > ISA has a WAIT instruction.  On VAX, there isn't one, so there
    > the code uses various schemes to recognize the idle loop of the
    > OS.  It needs to know what OS you're running, and of course it
    > needs to have sufficiently accurate logic matching what your OS
    > actually does.

    I wonder why VAX lacked that when the PDP-11 had it.  My emulated
VAX runs NetBSD/vax 9.3.

-Andy.