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VMIDLE is a small device driver that inserts a HLT instruction into the DOS idle interrupt chain. Under normal circumstances, VMIDLE will reduce CPU usage to zero while DOS is idle.

Once resident, the device driver consumes 32 bytes of memory. As far as I know, a resident DOS device driver can't be any smaller than 32 bytes, including the 18 byte header.

While intended to be used in DOS virtual machines, VMIDLE can be loaded on any system with an x86-compatible processor except for certain buggy Intel i486 DX 100 MHz parts.

To install VMIDLE, copy VMIDLE.SYS to an appropriate directory, e.g. C:\DOS, and add the following line to CONFIG.SYS:


If you have upper memory blocks available, add the following line:


You can also load VMIDLE.SYS from the command line using an appropriate device loader.

VMIDLE is Copyright (c) 2007, Trevor Scroggins and is licensed under a BSD 2-clause style license. Source code is included. Enjoy!
Trevor Scroggins,
Jun 8, 2014, 6:35 PM