turn on the OSD, to make sure that the clocks I set stay set?

On a guide about a month old in this forum, someone said:
"I turned on the OSD in rivatuner, so that I could make sure that the clocks I set were being run. EVGA Precision tuner has a similar OSD feature that can be used. The reason for this is that Nvidia cards have a feature that will automatically down clock the graphics card clocks if they are too high."

Here is his link with his instructions for configuring riva tuner http://www.overclock.net/nvidia-driv...hould-i-o.html

He says overclocking speeds will revert to stock speeds when stressing gpu unless you apply his settings to riva tunner. Is this true? If so then I should use rivatunner instead of precision and use his configuration instructions as outlined on link I provided in the first part of his thread before he actually get's to overclocking? And what is OSD? I thought I could just use precision and change the fan/clock speeds and be done with it. Are his settings he makes before changing clock speeds important to do?