PARAMETRIC EQ — signal-flow flowchart

Image rep algo 39 · slots 39 · unit 0 (I-RAM load 84) · family eq · confidence SOLVED.

parametric EQ: 5 bands x 2 channels, Direct-Form-I bilinear biquad (decoded to the bit); the reference program

105 words, 60 class-A coefficient multiplies (60 named), 0 instructions still opaque, 4 of 105 not yet decoded. Landmarks detected: 10 biquad DF-I section(s), 10 class-8 post-sum step(s).

flowchart TD
    N0["Stereo input (L / R)"]
    N1["5 bands &times; 2 channels<br/>Direct-Form-I bilinear biquad (SOLVED to the bit)<br/>per band: b1,b0,b2,&minus;a1,&minus;a2 &divide; a0, then make-up gain<br/>C-RAM[0x00..05]; rstcur re-reads the bank for channel 2"]
    N0 --> N1
    N2["per band (x5): BAND EMPHASIS FC, BAND EMPHASIS Q, BAND EMPHASIS G"]
    N1 -.-> N2
    N3["class-8 post-sum step &times;10 (rescale/round/saturate? &mdash; OPEN)"]
    N1 -.-> N3
    N4["VOLUME<br/>output level"]
    N1 --> N4
    N5["REV SEND<br/>to reverb bus"]
    N4 --> N5
    N6["Output"]
    N5 --> N6

    classDef io fill:#e8eef7,stroke:#33475b,stroke-width:1px,color:#111;
    classDef proven fill:#d7f0d7,stroke:#2e7d32,stroke-width:2px,color:#111;
    classDef measured fill:#dbe9fb,stroke:#1565c0,stroke-width:1.5px,color:#111;
    classDef inferred fill:#fdf0d5,stroke:#b8860b,stroke-width:1.5px,color:#111;
    classDef open fill:#eeeeee,stroke:#888,stroke-width:1px,color:#333,stroke-dasharray:5 5;
    classDef ctrl fill:#f3e8fb,stroke:#6a1b9a,stroke-width:1px,color:#111;
    class N0,N6 io;
    class N1 proven;
    class N2,N4,N5 ctrl;
    class N3 open;

Classic-topology match

Most likely textbook topology: Cascaded Direct-Form-I biquads (2nd-order sections in series).

Each band = one 9-word DF-I section ld.ta(0x13) · mac(0x12) · mac · mac.tb(0x14) · mac · mac.st tb · class-8 post · mac.st(makeup) · ld.st ta; two z⁻¹ state latches tempA/tempB; coefficients b1,b0,b2,−a1,−a2,makeup.

Instruction hint: ACT 0x13 = load state tempA, 0x12 = MAC, 0x14 = MAC+store tempB; tempA/tempB ARE the biquad z⁻¹ states. This is the ISA reference program.

UI parameters (MEASURED, notes/kn5000-dsp-paramlist.md): (BAND EMPHASIS FC, BAND EMPHASIS Q, BAND EMPHASIS G) x5, VOLUME, REV SEND.

Per-instruction detail: ../disasm/prog39_parametric_eq.dsm. Confidence legend and method: README.md. Narrative: the MAME development blog, KN5000 effects-DSP series (Parts 78-84). Reference: the project docs site, /effects-dsp/.