Apple System Profiler performs a calculation to determine processor clock speed based on 66.7 MHz system bus speed (66.7 * 5 = 333.5 MHz). When it calculates a value of 333.5 MHz, for example, it rounds up to the next whole digit (334 MHz in this case). Apple conservatively advertises this processor as 333 MHz because it is not quite 334 MHz.
Currently, the hard disk drive industry measures disk capacity as 1MB = 1,000,000 bytes (1000 * 1000). The Mac OS Finder and Apple System Profiler measure disk drive capacity as 1MB = 1,048,576 bytes (1024 * 1024).
For example, if you take a 4.0 GB hard drive (4000776192 bytes = total size), the following interpretations can occur: If you divide the total bytes by 1,048,576 bytes, the Mac OS Finder and Apple System Profiler show this space as follows: 4000776192 bytes = 3815.4375 MB = 3.7 GB If you divide the total bytes by 1,000,000 bytes, the hard disk drive industry measures drive capacity as follows: 4000776192 bytes = 4000.776192 MB = 4.0 GB
For more information, see the related article:
Knowledge Base article 30065: "
Macintosh Hard Drive: Is It Missing Space?"