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From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr)
Newsgroups: comp.sys.dec
Subject: Re: MicroVax hardware compatibility
Message-ID: <1990Aug24.012018.485@spcvxb.spc.edu>
Date: 24 Aug 90 05:20:18 GMT
References: <12927@hydra.gatech.EDU>
Organization: St. Peter's College, US
Lines: 25

In article <12927@hydra.gatech.EDU>, bb16@prism.gatech.EDU (Scott Bostater) writes:
> I have some software written for VMS version 4.6 that makes use of a PDP-11
> backward compatibility mode.  I want to run the software on a microvax.  Is
> this backward compatibility mode going to shoot me in the foot?  

  The correct answer is "it depends". If your software did it the documented
way and used the RSX AME (Application Migration Executive), it will run on
the MicroVAX II *if* the II has the AME installed.

  On the other hand, if your software does it the way V4's TECO did it (by
providing it's own AME and kicking the CPU into compatibility mode) it won't
work, as the II doesn't have such a mode.

  Also, earlier versions of the AME did not supply a software emulator for
the CPUs that didn't have compatibility mode. The current version (V2.4) does
provide a software emulator.

  You can expect the software to run slower on the II, since the PDP-11 is
being emulated in software. Only the 700-series had hardware compatibility
mode. (Yes, I know about the 8600/8650. Those were planned to be called the
790/795, and are really 700-series CPU's).

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381