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You should know that the Mean Time Between Failure (MTBF) is simply the inverse of the failure rate for an exponential distribution, while the Failure in Time (FIT) rate is 10^9 x failure rate as is stated in the following way:
MTBF = 1/failure rate
If FIT = 15.1, then MTBF = 10^9/15.1 = 66225165
The FIT values can be found in the Production Release Qualification (PRQ) Report of each processor.
You should find the information that may help in section 4.3, on page 10 of the Intel Atom® Processor E3915, E3930, E3940, and E3950 Qualification Report document # 612161. You can find it when you are logged into your Resource and Design Center (RDC) privileged account on the following website:
You should fill out the RDC Account Support form to process your account update request or report any inconveniences with the provided site. You can be found on the following website: