VAX-11's compatibility mode

Guy Harris guy at rlgvax.UUCP
Tue Feb 5 11:27:45 AEST 1985


> I'm trying to use the vax-11' compatibility mode on an object code written for
> a pdp-11/45 computer, and getting the message "file compiled with separate i/d
> space".
> Is there anybody out there who knows about the compatibility mode and the
> meaning of that message?

The meaning of the message is that PDP-11 compatibility mode doesn't
support separate I/D space.  (Heck, says DEC, none of *our* software uses
it - well, RSX-11M+ does, but it didn't exist when they did the 780).

> What should I do about it?

Find a PDP-11 to run your program on (the microVAX doesn't have compatibility
mode either - I have no idea whether DEC plans to support it indefinitely
or not).

> Where can I get good information about the compatibility mode?

Get a copy of the VAX-11 Architecture Reference Manual (EK-VAXAR-RM-001)
from your local DEC office.  (List of things not supported in compatibility
mode, from that manual:

Privileged instructions
"Special instructions" such as traps and WAIT (well, EMT and TRAP work,
since PDP-11 programs can make system calls both under VMS and UNIX
compatibility modes)
Access to internal processor registers (i.e., referencing them with
addresses like 0177776 for the PSW)
Direct access to trap and interrupt vectors
Direct access to I/O devices
Interrupt servicing
Stack overflow protection
Alternate general register sets
Any processor mode other than user and separate I and D spaces
Floating point instructions)

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy
> 
> Thanks,
>             Yadran

*** REPLACE THIS LINE WITH YOUR MESSAGE ***



More information about the Comp.bugs.2bsd mailing list