How are Video Card clock speeds Measured?

[RezidentSeagull]

So, the title's kinda vague, but what I'm trying to figure out is how are reviewers like Linus and Luke measuring clock speed, and which measurements they're reporting. I'll try and clarify what I mean.

 

For example, my overclocked graphics card (a Gigabyte Windforce GTX 970) in GPU-Z lists the GPU clock as 1324 MHz and the Boost clock as 1463 MHz on the Graphics Card tab.

 

However, when I'm using MSI Kombustor to torture test my video card, both MSI Afterburner, as well as the GPU Core Clock sensor in GPU-Z report ~1525 MHz after the temperature levels off after a few minutes.

 

So, which measurement would I use when doing rough comparisons with other graphics cards? Which measurement would be used in the overclocking google doc, for example? Mainly, I'm just interested in knowing how to roughly but fairly compare my overclock attempts to other overclockers.

[kiwibacon]

cycles per second?

[incarnate]

If I'm not mistaken gpu-z reports the stock clock speeds. Msi reports current