The answer lies in the prefixes. Let's say your processor is running at 3,500 MHz, but you want to show that in GHz. Since Hz is an SI unit, one uses the SI prefix system where the G stands for ...

New unit measurement prefixes are added to the metric system The mass of the Earth can now be measured as 6 ronnagrams rather than 6,000 yottagrams. An electron's mass can now be said to be about ...