[Simh] Batch vs interactive

[Villy Madsen]

One of the issues that I have run up against running OPENVMS on simh is that the tuning parameters for the OS are not optimal for todays high speed disks.

If you run a IO intensive application (like synching mirrored disks under VMS) the IO operations can easily chew up all of the emulated cycles available.  I had given some thought to changing the disk drivers so that there were built-in delays to more accurately represent that dasd that was availble for the 3900 - but decided that it wasn't worth the effort...

Villy

----- Original Message -----
From: Gary Lee Phillips <tivo.overo at gmail.com>
Date: Monday, May 17, 2010 10:09
Subject: Re: [Simh] Batch vs interactive
To: simh at trailing-edge.com

> The answer depends on what machine you are emulating and with what
> operating system. Something like a VAX with OpenVMS has a lot of
> tuning parameters within the operating system for balancing 
> batch and
> foreground priorities. Most systems that had simultaneous batch and
> interactive operation were set up in this way. But the controls are
> internal to the operating system software, not to the hardware itself
> and therefore not in the purview of SIMH settings.
> 
> Or did you mean that you are letting something run on a SIMH emulation
> and it gets in the way of doing other things on your host machine?
> There is a setting to control the percentage of the host CPU 
> that is
> used by most SIMH emulators I've tried, though I don't know 
> whether it
> is active in all of them:
> 
> SET THROTTLE xx%
> 
> This command given at the SIMH command prompt limits the amount 
> of CPU
> that can be taken up by the SIMH emulation at any time to xx% of the
> whole.
> 
> It will not, however, balance between batch and interactive processes
> running within the emulation. Those will both be slowed down by an
> equal amount. Tuning that balance requires internal settings in the
> emulated environment.
> 
> --Gary
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