18.104.22.168. Mitigated FIT
The Projected SEU FIT by Component Usage report's w/ECC column represents the FPGA's lowest guaranteed, provable FIT rate that the Intel® Quartus® Prime software can calculate. ECC does not affect CRAM and flipflop rates; therefore, the data in the w/ECC column for these components is the same as the in Utilized column.
The ECC code strength varies with the device family. In devices, the M20K block can correct up to two errors, and the FIT rate beyond two (not corrected) is small enough to be negligible in the total.
An MLAB is simply a LAB configured with writable CRAM. However, when the Intel® Quartus® Prime software configures the RAM as write enabled (MLAB), the MLAB has a slightly different FIT/Mb. The Projected SEU FIT by Component Usage report displays a FIT rate in the MLAB row when the design uses MLABs, otherwise the report accounts for the block's FIT in the CRAM row. During compilation, if the Intel® Quartus® Prime software changes a LAB to an MLAB, the FIT accounting moves from the LAB row to the MLAB row.
The w/ECC column does not account for other forms of FIT protection in the design, such as designer-inserted parity, soft ECC blocks, bounds checking, system monitors, triple-module redundancy, or the impact of higher-level protocols on general fault tolerance. Additionally, it does not account for single event effects that occur in the logic but the design never reads or notices. For example, if you implement a non-ECC FIFO function 512 bits deep and an SEU event occurs outside of the front and back pointers, the application does not observe the SEU event. However, the report accounts for the full 512 bit deep memory and includes it in the w/ECC FIT rate. Designers often combine these factors into general deflation factors (called architectural vulnerability factors or AVF) based on knowledge of their design. Designers use AVF factors as low (aggressive) as 5% and as high (conservative) as 50% based on experience, fault-injection or neutron beam testing, or high-level system monitors.
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