Greetings...
While your Youtube demo of the HIS HD 4670 etc. is a great and fast paced video, there's some terminology that needs addressing. Since this doesn't appear to be some marketing department that doesn't like those bewildering "technical" terms - it's time to get them straight!
It seems that the reviewer has a bit of a problem understanding the difference between "speed," "frequency" or more specifically "clock rate." Hint: the three are NOT the same thing - and they never have been! When you head down the road and look at your speedometer, you don't measure your rate of movement as a frequency - for example, 3 kHz or 3 GHz. Conversely, you don't tune your radio or satellite receiver to a different speed.
Without repeating the text, consider:
http://wiki.answers.com/Q/Is_speed_of_cpu_is_measured_in_hertz
Mr. Mentor