Huw Davies huw.davies at
Wed May 1 17:20:42 CDT 2019

> On 2 May 2019, at 07:47, Eric Smith via cctalk <cctalk at> wrote:
> The VAX 8600 and 8650 were the last VAX models to have PDP-11 compatibility
> mode, so if the purpose of VMS 4.0 was to support the 8600, I would expect
> it to still contain compatibility mode support. VMS versions at least as
> late as 5.2 still supported the 8600. I don't have firsthand experience, as
> the only 8600 I used ran BSD.

I seem to recall that there was a software implementation of compatibility mode to allow PDP-11 code to be run on VAX hardware that didn’t have it natively.

At one stage I used to manage a very eclectic mix of VAX systems, including 11-780, 11-785, 8650, 8700, 8800, 8820, 8840, 6300, 6600, 7740.

Huw Davies           | e-mail: Huw.Davies at
Melbourne            | "If soccer was meant to be played in the
Australia            | air, the sky would be painted green" 

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