The results you are getting are expected. Keep in mind that the fsb on the system works using quad pumping which allows four transfers per cycle, so in this case, 99 mhz multiplied by 4, results in 396 mhz (which would be pretty close to the 400 mhz). So what the software is detected integrated the host frequency, which determines the FSB (Front Side Bus).
For more information on how the FSB (Front Side Bus) works you may refer to this site:
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