Johnny Billquist bqt at softjar.se
Wed Jul 14 13:28:00 CDT 2010

Ethan Dicks <ethan.dicks at gmail.com> wrote:

> On 7/14/10, Jerome H. Fine <jhfinedp3k at compsys.to> wrote:
>>  In addition, does anyone know  of any systems currently running
>> which support RTEM-11 features which allow RT-11 programs
>> to run in that environment?  My assumption is that VMS on a VAX
>> supported RTEM-11 at some point, but perhaps (if I am correct)
>> the RTEM-11 support was not  continued with
>> more recent versions of VMS on the VAX and most definitely VMS on the
>> Alpha.  Can anyone comment on these questions?
> Based on the vague reference at
> http://s-and-b.net/help?key=RTEM~Release_notes&title=VMS Help&referer=
> and what I know of VMS and DEC hardware, I'd think that RTEM-11 would
> require a VAX processor with "compatibility mode", i.e., a "VAX-11"
> processor.  The primary models would be the 11/78x, 11/750, 11/730 and
> 11/725 (I don't recall if the VAX 86xx still had "compatibility mode"
> or not, but it should be easy to check).  MicroVAXen and such did not
> have it, and Alpha processors certainly did not have it.
> That being said, I have no experience with RTEM-11, but I would be
> surprised to learn it ran on a machine made after about 1986 or so.

RTEM might be something else than RTEM-11, which was a software product 
for RSX. Just google for RTEM-11, and you'll find some references for it.

However, I wonder about RTEM for VAX. It's certainly possible, but I 
can't find any other reference to it, and DEC's old SPDs, especially 
those with software version compatiblity matrixes, are usually pretty 
good as a way of finding out what software existed.

As for PDP-11 compatibility in VAXen, yes, the 86x0 machines have that. 
Those were the last, however.

For all other VAXen running VMS, if you wanted to run RSX software, you 
needed a PDP-11 emulator product for VMS, which was available, in 
addition to the RSX additions for VMS, which was also a separate 
product. That thing was supported up until fairly recently, though.
But again, that's for RSX stuff...


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