Alphaservers for free in Athabasca, Alberta

Antonio Carlini a.carlini at
Sun Aug 11 14:14:06 CDT 2019

On 06/08/2019 16:38, Jon Elson via cctalk wrote:
> The VAX 11/780 definitely had PDP-11 emulation, apparently in the 
> microcode.  I'm kind of guessing the 750 and 730 also had this. As far 
> as I know, no later machines had hardware (microcode) emulation, and 
> did it all by software.  It didn't take very long for DEC to recompile 
> all the VMS utilities into native VAX executables.  I think we started 
> with VMS 3.x and very quickly updated to a 4.1 VMS version.  I was not 
> aware of any PDP-11 code in them, but I did not look very closely.
The VAX-11/7xx all implemented PDP-11 compatibility mode, I think. 
That's VAX-11/780, VAX-11/725/730, VAX-11/750 and VAX 8600 (which was at 
one point going to be VAX-11/790). The VAX 8650 was a souped up VAX 8600 
[1] so that almost certainly has PDP-11 compatibility mode. Nothing else 
does. The VAX 82x0/83x0/85x0/8700/8800/88x0 don't.


[1] Actually I think that the VAX 8600 ("Venus") was slowed down to get 
it reliable enough to ship at all (and it was quite late at that, iirc). 
The VAX 8650 ("Morningstar") followed just over a year later and was 
(more or less) what the original VAX 8600 should have been.

Antonio Carlini
antonio at

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