1,000+ ASIC Interview Questions: SystemVerilog, UVM & RTL

DescriptionQ901

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Q901FWAMDASIC interview problem

Classify ECC counter changes

TechniquesSiliconReliabilityDebugClassifyEcc

DifficultyMedium

TopicPost-Silicon Validation

LanguageC++

Requirements4 checkpoints

Problem

A monitor compares two AMD-style reliability, availability, and serviceability (RAS) snapshots with monotonic error-correcting code (ECC) counters. Write the C++ function that validates the samples and returns the required severity.

Starting declarationC++

enum Sev { ECC_OK, ECC_WARN, ECC_FATAL, ECC_BAD };
Sev ecc_delta(uint64_t c0,uint64_t u0,uint64_t c1,uint64_t u1,
uint64_t warn_threshold);

Example input and output

Use this case to check your interpretation

Input

c0 = 10, u0 = 0, c1 = 13, u1 = 0, warn_threshold = 3.

Output

ecc_delta returns ECC_OK.

Explanation

No counter regresses, the uncorrectable delta is zero, and the correctable delta equals rather than exceeds the warning threshold.

Requirements (4)

If either new counter is less than its old counter, return ECC_BAD.
If u1-u0 is nonzero, return ECC_FATAL regardless of the correctable delta.
Otherwise return ECC_WARN when c1-c0 is strictly greater than warn_threshold.
Return ECC_OK for every remaining case, including a correctable delta equal to the threshold.