Weighted Knobs
ConceptWeighted knobs are test-level weighted controls used in a hierarchical constrained-random microcode instruction generator to bias the distribution of generated opcode categories and instruction mixes.
First seen 5/26/2026
Last seen 5/31/2026
Evidence 2 chunks
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WIKI
Definition
Weighted knobs are weighted values exposed at the test or upper-sequence layer of a constrained-random instruction generator. In the described AMD/Synopsys microcode stimulus generator, tests used these weighted values to direct the generator toward a required mix of instructions, and the constraint solver applied the weights to control the distribution of opcode types that were created.
Role in generator architecture
NEIGHBORHOOD
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2 connectionsHierarchical constrained-random test generation uses weighted knobs to control instruction distribution.
The opcode generator uses weighted knobs to control instruction distribution.
LINKED ENTITIES
3 linksSystemVerilog Random Sequence Construct uses The evidence states that the upper layer was implemented using a SystemVerilog random sequence construct with weighted knobs.
Synopsys VCS Constraint Solver applied_by The evidence states that the constraint solver directly applies the weights to the generator layer to control opcode-type distribution.
Opcode Generator controls_distribution_in The evidence describes an opcode generator whose upper layer uses weighted knobs to control distribution of high-level items.
CITATIONS
7 sources7 citations — click to expand
[1] Weighted knobs controlled high-level distribution in the generator upper layer Generating AMD microcode stimuli using VCS constraint solver
[2] Tests used weighted values to direct the generator to the required instruction mix Generating AMD microcode stimuli using VCS constraint solver
[3] The constraint solver applied weights to control distribution of generated opcode types Generating AMD microcode stimuli using VCS constraint solver
[4] Opcode categories in the multi-class generator mapped to knobs or weights in the test interface Generating AMD microcode stimuli using VCS constraint solver
[5] The upper-layer random sequence was controlled by knobs only and chose the opcode category first Generating AMD microcode stimuli using VCS constraint solver
[6] Direct test-layer control of lower-level subclass items would likely require a wrapper class and two-phase generation Generating AMD microcode stimuli using VCS constraint solver
[7] Hierarchical partitioning of opcode constraints into base and subclasses reduced memory requirements and increased performance Generating AMD microcode stimuli using VCS constraint solver