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microarchitectural state

Concept

Microarchitectural state is the implementation-level processor state, such as predictor, cache, TLB, FIFO/backpressure, and other internal structures, that can influence execution timing and internal paths while being distinct from architectural program state. In the supplied evidence, it is important mainly for simulation-based processor verification: Logic Fuzzer deliberately perturbs such state or related control signals to reach atypical states and expose bugs that ordinary tests may miss.

First seen 5/27/2026
Last seen 5/28/2026
Evidence 4 chunks
Wiki v2

WIKI

Overview

Microarchitectural state is the processor-internal state associated with implementation structures and control behavior, as distinct from the architectural state visible to the ISA-level model. The evidence contrasts Dromajo checkpoints, which are snapshots of a processor's architectural state, with caches, TLBs, and other memory elements whose reset contents can lose microarchitectural states from which bugs might manifest. [C1]

In the Logic Fuzzer work, microarchitectural state matters because a processor bug may require a difficult-to-reach internal condition before it produces an architecturally visible mismatch against a golden model. The paper describes the key simulation-verification challenge as developing a code sequence that brings the processor into a buggy microarchitectural state that results in an inconsistent architectural state. [C2]

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Logic Fuzzer ← uses 100% 1e
Logic Fuzzer randomizes microarchitectural states to expose bugs.

CITATIONS

10 sources
10 citations — click to expand
[1] The evidence distinguishes architectural checkpoints from internal caches, TLBs, and other memory elements whose reset contents can lose microarchitectural states. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[2] Simulation-based verification may require a code sequence that brings the processor into a buggy microarchitectural state that later causes an architectural mismatch with a golden model. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[3] Examples of relevant internal structures and signals include branch predictor tables, BTB entries, Return Address Stack state, instruction-cache tag/data arrays, cache and TLB entries, reorder-buffer full or stall behavior, and FIFO or handshake backpressure signals. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[4] Fuzzed BTB entries can supply false or random predicted addresses and can potentially create iTLB page faults on a mispredicted path; Logic Fuzzer can also insert instructions in the mispredicted path. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[5] Outlier bugs may evade random instruction streams and directed tests because the required sequence of events is too complex, and may require exercising the design outside normal flow or operating parameters. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[6] Logic Fuzzer randomizes selected states or control signals that should not affect correctness, such as ROB full or stall behavior and branch predictor tables, and can change cycle count without corrupting functionality or program order. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[7] In the reported evaluation, Dromajo alone found nine bugs, while Dromajo enhanced with Logic Fuzzer exposed thirteen bugs without creating additional verification tests. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[8] Logic Fuzzer table mutators mutate RTL memories; branch predictor tables can be fuzzed freely, and other examples include random invalidation of cache or TLB entries and value fuzzing of already invalid entries. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[9] Checkpoint-based simulation can lose microarchitectural states because caches, TLBs, and other memory elements start from reset state; table mutators can partially close the gap by pre-populating or randomizing tables. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...
[10] Logic Fuzzer may create microarchitectural states that no real program could reach; resulting co-simulation failures are red flags to be proved or disproved, and the paper's reported bugs were confirmed by designers. [PDF] Effective Processor Verification with Logic Fuzzer Enhanced Co ...