[Simh] Problem booting an emulated VAX-11/780 from a Massbus disk drive

[Peter Allan]

I started this thread over on comp.os.vms in case anyone knew of VMS cause
of my problem, but it seems to be a problem with simh.

have been trying to set up the VAX780 emulator in simh to boot VMS 4.6 from
an RP06 disk drive and I have failed.

My tests have been the following.

I installed VMS 4.6 (and 4.0 and 4.2) on an RP06 drive. When I try to boot
from the RP06, then VMS starts up, displays a line like

    VAX/VMS Version  KG  15-Jun-1987 10:00

and sits there forever. The "KG" is because I have not yet been able to
apply the mandatory update. Clearly the 780 is booting from the disk since
it displays the one line message.

If I boot with the command

    b rp0/r5:1

then I get into SYSBOOT, but everything appears to be fine. Typing
"CONTINUE" returns to the hung state.


Next I tried installing VMS 4.6 on to an RA81 disk drive. This works fine,
so I copied the contents of the RA81 to an RP06 drive using stand alone
backup and tried booting from the RP06, but still the system hung during the
boot process. So the problem appears to be with the RP06 drive, not with VMS
or with the installation procedure.

I tried changing the RP06 disk type to all other possible Massbus disk types
(RP04/05/07, RM02/03/05/80) and installing VMS 4.6. These all act in the
same way as the RP06.

However, I have also tried to install VMS 5.0 and VMS 7.3 on to an RP06.
This works fine!

So, the problem occurs with the specific mixture of a Massbus disk drive and
VMS 4.x (I have tried x = 0, 2, 6)


I have just examined the code of pdp11_rp.c, which contains at the end of
the file:


/* Boot routine */

#if defined (VM_PDP11)

<< lines deleted >>

t_stat rp_boot (int32 unitno, DEVICE *dptr)
{

<< code concerned with booting from an rp type drive >>

#else

t_stat rp_boot (int32 unitno, DEVICE *dptr)
{
return SCPE_NOFNC;
}

#endif


Is this code really only needed for a PDP11, or does it apply to a VAX780 as
well? I tried changing VM_PDP11 to VAX_780, just for a test, but I got some
error messages, so I thought I better ask for help rather than blundering
about in the code.

I am very confused since the vax780 emulator WILL boot successfully from a
Massbus disk for VMS 5.0 and 7.3, but it does not for VMS 4.0, 4.2 and 4.6.

Can anyone shed any light on this - or even offer a solution?

I have been doing nearly all of this on Linux (CentOS 5.5), but I did try to
install VMS 4.6 on to an RP06 using the Windows version of the system "just
in case". That gave the same problem.

Peter Allan
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