VAX PDP11 compatibility mode

From: Bill Pechter <>
Date: Thu Jan 31 05:15:48 2002

> > The only use of the vax11's pdp11 compatibility mode that I've ever
> > heard of was to run RSX-11 binaries under VMS.

Another was the RTEM RT11 emulator which gave you (by default) a PDP11/40
with EIS running RT11 V5 (IIRC) emulated on the Vax. I used this at DEC
for sysgens for my PDT 11/150 and wrote out the floppy on the RX01
console floppy with FLX/Exchange.

> I think VMS 1.0 used it because it was not really ready to ship (what a
> suprise). The RCS VAXgeek said that some old PDP-11 code was
> kludged in with a big hammer (and the compatibilty mode) to get the early
> VMS to work. The kludges were dropped shortly afterwards.

Well, the kludges were dropped slowly since a lot of the utilities were
running in compatibility mode up through VAX/VMS 3.x.

When we hit 4.x (IIRC) MCR SYE and FLX went away to be replaced with
Anal/error and exchange.

> William Donzelli


  d|i|g|i|t|a|l had it THEN.  Don't you wish you could still buy it now!|
Received on Thu Jan 31 2002 - 05:15:48 GMT

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