From: xbitlabs
Let me introduce to you the actual hero of this review: Intel Pentium 4 2.4C processor. It is not just an ordinary Pentium 4 (the letter C after the frequency is not a slip of the tongue or typo), as it boasts significant innovations: ...
* By launching new processors supporting 800MHz bus, Intel announced its new approach to the CPU voltage formation. The company won’t set a fixed voltage, but will suggest a range of voltages. During the actual production stage all processors are divided into four classes. Each class has a certain voltage from
1.475 to
1.55V, depending on the die quality. Of course, models with the minimal core voltage are most interesting for overclockers as they have the highest speed-up potential. However, there is no marking on the processor telling its voltage, so you cannot know the voltage until you install the CPU into the mainboard.