[Simh] Update to VAX throttle

[Villy Madsen]

I have made some updates to the code:

scp.h has been modified so that the whole thing works running under *ix. 
 Thanks to David Holland for that.

VAX_CPU changes are cosmetic only - removing some commented out debug code 
that I had added.

DN_11 changes to throttle the no_queue wait down more as the emulator is 
slowed.

Throttle has some changes in it.  I was at times assigning a minimum value 
for the throttle that really made the system too slow.  The logic has been 
changed to hopefully prevent that.  It will now try to get a minimum value 
somewhere in the range of .35 to .75 vups.

I also added some code to handle the situation where this process "loops 
up".  The easy fix was to add a retry counter and if it runs out to crank 
the emulator back up to fill output.  If you run into this problem, email 
me the startup log and I'll see what I can do.

The makefile has the DN-11 module added in for the VAX and also changes the 
optimization for W32 compiles from 0 to 2  (-O2 vice -O0).  Read the notes 
in the makefile wrt issues with -O2.


VAX.ZIP contains a w/32 exe and the complete source code for the changed 
modules.  It's small enough that I couldn't be bothered with running diff.

code can be found at http://68.150.97.212/simh.  The system isn't up all 
the time, but you shouldn't have any problems getting it.  It is up most 
evenings during the week (GMT-7) and most of the time over the weekends. 
(please remember to refresh your cache!)


On another note, I tried rewriting the memory module to directly address 
the bytes and words - vice the shift and mask process.  I was somewhat 
surprise to find that there was no measurable difference in performance. 
 That speaks a lot for modern technogy.  The big difference that I thought 
I saw originally was due to my benchmark being against the original 
distributed w32 executable - which has Bob has pointed out has no 
optimization and all the debugger code included...

Please feel free to post any comments or suggestions.  Also please let me 
know if you are using throttle.

Villy

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