[Simh] VAX Throttle

[Villy Madsen]

Throttle is a package the allows the SIMH VAX simulator to be throttled 
based
upon the VAX processor activity.

It requires a modified VAX (W32)  simulator and some OPENVMS programs
which are available at

http://68.150.97.212/SIMH

This system is not always up - but you shouldn't have any problems getting 
to
it.  If you do - email me and I will send them via E-Mail.

The source for the VAX simulator will be published as soon as I get it
cosmetically cleaned up...

The package works by inserting 1ms sleeps into the instruction execution 
cycle every N instructions.  N is controlled an application running on the 
vax that runs every 2 seconds and collects usage stats.  The simulator is 
throttled up and down in an attempt to maintain CPU utilization between 25% 
and 80%.  The source (and executables) for this routine is included.

Throttle communicates with the simulator using an IO address normally 
reserved for use
by the DN-11 autodialler interface.  Since I suspect that no-one in their 
right mind would ever want to use such an animal, I felt that this was a 
safe address to use. (I did use them back in the early '80s  they worked ok 
once we got someone to write a device driver for us, (and fixed a minor 
glitch - of course any glitch in a device driver causes a 
 (*&(*&()*&()*&(*&(*&^%$^%!!!!).  - As long as we kept lots of spare 
autodialers....  These expensive devices from Western Electric had a nasty 
tendancy to cook themselves!)

Throttle tries to set a min throttle point at about .5 to 1 VUP.  On a 3ghz 
P4 this doesn't event move the meter....

Try it out and let me know what you think.  I will post the source as soon 
as I figured out  all of the changes (bad bad bad application developer!!!)

Villy


Villy Madsen
www.members.shaw.ca/villy.madsen