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Connectix/Virtual PC DOS aplpication takes 100% CPU

Posted on 2006-10-27
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Last Modified: 2013-11-15
Does anyone know how to throttle DOS applications in a virtual environment so that they let go of the CPU when idle?

I have tried the idle.com install but it doesn't seem to do the trick.  After installing it, I have to manually run the idle.com command then the DOS application gives up the CPU but I thought it was supposed to do it on its own...

Any tricks would be appreciated!

Thanks!
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Question by:SYSadmin22
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by:scrathcyboy
ID: 17824102
DOS apps are not designed to be multi-threaded, meaning, they will run all the time, at full CPU utilization.

However, if you create a PIF for the DOS app, then you will be able to fine tune the application to act according to certain memory and utilization models.  When you do, you get a multi-tab layout with General, Program, Font, Memory, Screen, Misc and Compatibility tabs.

In the compatibility tab, choose, "Run this program in compatibility mode" and choose NT or better still, 2000.  This will force the OS to time slice the application and not allow it 100% CPU utilization.

Also explore the other tabs on that interface, including memory and other tab settings, and you will find that you can limit it as best you can.  Anything more than this cannot be done, so work on that.
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by:SYSadmin22
ID: 17825596
Thanks for the info!

I have never heard of a PIF...  I will research that and see if I can figure it out.

Can you explain or provide some info on that?

Thanks!
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by:SYSadmin22
ID: 17825624
OK, that was easy to find.

I don't know if this is an option for me because the DOS application that I'm referring to is actually a true 16 bit DOS app that is running in it's own virtual machine in the old version of Mcrosoft Virtual PC, Connectix.

I think the PIF will only work if the dos app is running inside a 32 bit application.

Am I off the mark here?

Thanks
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by:scrathcyboy
ID: 17827393
Yes you are off the mark.  A PIF is a WINDOWS ENVIRONMENT specification to run ANY DOS app from, and it includes 16 bit, since there is no such thing as a DOS 32 bit app -- dos does not do 32 bit.

The important thing about a PIF is that you can change ALL the windows environment variables to match what the DOS app need to use to run correctly.  You will find that this is EXACTLY the way you need to go to get your DOS app to work under the XP environment.
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Author Comment

by:SYSadmin22
ID: 17843174
I'm not sure who's confused here but I'll try to explain the situation here.

First, I'm not sure if you know what Virtual PC is but it's like VMWare and this dos app is running inside this image.  There is no windows XP, 2000 or NT4 inside this image just a DOS app so I can't exactly log into it and click an executable or shortcut to customize the application.  So there is no windows environment to adjust unless you can tell me how to modify virtual PC...

Secondly, I have resolved this myself by Pausing Virtual PC when not in use which in essence sends the commands to give up the CPU.  I'm happy with this since I'm getting rid of the DOS app in a few months.

Thanks for the input.
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by:scrathcyboy
ID: 17847102
"So there is no windows environment to adjust unless you can tell me how to modify virtual PC"

Wrong, the environment is customized at the time you run the application, you just have to provide the right variables, which is what I have been telling you all  along.  I am not confused here, perhaps you see a big difference between running a DOS app under a windows shell, vs. running the DOS app in a VM environment.  In practicality there is NO difference at all, all you must do is customize the environment.  Since you seen to have solved the situation along the lines I said, I suggest you close the question by awarding to the most accurate answer.  Good luck
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by:SYSadmin22
ID: 17847196
OK, I'm confused...  Please provide me with the instructions on how to accomplish what I need to do and I'll gladly award you the points!

Thanks again!
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