I ran both DesqView and DesqView/X and I never saw any performance degradation while running DOS apps. If you ran Windows under it, it would suffer because of

I ran both DesqView and DesqView/X and I never saw any performance degradation while running DOS apps. If you ran Windows under it, it would suffer because of the poor (at the time, non-preemptive) scheduler. Windows was/is by its own definition, an "ill behaved" application.