[Simh] Interdata Emulation

[Davis Johnson]

I've just come accross the Interdata emulators, and have had a week or 
two of play.

I can currently boot either the Version 7 unix from trailing-edge.com or 
OS/32MT R08-02 from my personal collection. I have been having 
difficulty getting simulated disc working. At first I thought I was 
tracking down what appeared to be a lost interrupt but that is not the 
case. I'm not getting an interrupt because the driver is getting a 0x08 
(device not ready) from the disc device address. The Interdata disc 
(always disc. never disk. I don't know why. I now have a hard time 
typing disc) controler occupies five device addresses - a controler 
address and four disc addresses.  I get a good status from the controler 
and unavailable from the disc.

I suspect I may be doing somthing wrong when attaching the disk. (I 
can't type "disc" any more.) The Interdata SIMH documentation says that 
a non-attached disk appears as "not ready". My command file looks like:

    set cpu 832
    set dm0 msm300
    att -e dm0 dm0.dsk
    att mt0 boot.tap
    d 78 85a18540
    set cpu hist=100
    set br 954a
    boot mt0

When I peer into the sense status instruction emulation with I find:

    case IO_SS:                                         /* status */
        if ( uptr->flags & UNIT_ATT) t =
            ((uptr->flags & UNIT_WPRT)? STD_WRP: 0) |
            (sim_is_active (uptr)? STD_NRDY: 0) |
            (uptr->STD & STD_UST);
        else t = STD_NRDY | STD_OFFL;                   /* off = X'09' */
        if (t & SETD_EX) t = t | STA_EX;                /* test for ex */
        return t;

Where uptr->flags does not have UNIT_ATT set. I'm thinking I somehow 
don't realy have the disk attached properly. I'm begining to suspect an 
operator head space problem here.