Course: Arithmetic circuits -- adders, multipliers, CORDIC, floating point (9x3, hardware track) #1488

Parent epic: #1476

Course id: arithmetic-circuits
Audience: hardware engineers (RTL / FPGA / ASIC).
Prerequisites: Course 1 module numbers; Course goldenfloat recommended.

Why this course

Arithmetic circuit design is a classic university course and a core interview topic. The repo has ternary adders, hybrid arithmetic, bigint, and correctly rounded GoldenFloat add/multiply (gft_add_rne, gft_mul_rne), but no course on how adders and multipliers are built and what they cost on a 7-series chip.

What already exists in the repo (grounding)

• ternary/ternary_full_adder.t27, ternary_ripple_adder.t27, hybrid_arithmetic.t27, bigint.t27, hybrid_bigint.t27
• ternary/gft_add_rne.t27, gft_mul_rne.t27, gft_recip.t27, gft_madd.t27
• fpga/mac.t27
• Missing: binary adder families, multipliers, CORDIC, divider specs

Decomposition: 9 modules x 3 lessons

Module 1 -- adders: adding fast

Module 2 -- carry-chains: what the FPGA gives you

Module 3 -- multipliers: multiplying

Module 4 -- dsp-blocks: hard multipliers

Module 5 -- division: dividing and roots

Module 6 -- cordic: rotations with shifts and adds

Module 7 -- fp-add: floating-point addition

Module 8 -- fp-mul: floating-point multiply and fused ops

Module 9 -- big-numbers: beyond the word

Specs that do not exist yet (write in gHashTag/t27 first)

• arith/adders.t27 -- ripple, lookahead, prefix, carry-save, CARRY4 model
• arith/multipliers.t27 -- array, Booth, Wallace/Dadda
• arith/divider.t27 -- restoring, non-restoring, SRT
• arith/cordic.t27 -- rotation and vectoring

Honesty notes and traps

• Every cost figure must come from a yosys/nextpnr run on a named part, not a textbook.
• FP lessons reuse GoldenFloat specs; cross-link the goldenfloat course instead of re-teaching the formats.

Acceptance criteria

• specs/course/<id>.t27 + <id>-ru.t27 exist, registered in specs/course/courses.t27, built by course-from-spec.mjs (recipe: specs/course_recipe/course-27.t27).
• Exactly 9 modules x 3 lessons = 27 lessons; every lesson names one widget and one spec.
• Every lesson spec compiles AND its test blocks pass in the reader's browser (blocked by the browser-runner issue), or the lesson says plainly that it is a recorded tri cast and links the recording.
• Every number on a page comes from real tool output named in the widget's DATA_SOURCES (yosys / nextpnr / board run / spec test). No invented figures.
• Board named on every hardware page (Wukong xc7a200tfgg676 vs AX7203 xc7a200tfbg484 vs Arty A7 / XC7A100T).
• Black-and-white share cards and SEO pages generated for all 27 lessons (EN + RU).
• The course PR carries a blog post: EN body + RU ruBody.
• Lessons that need a spec that does not exist yet are listed as sub-tasks (spec first in gHashTag/t27, then copied here).

Blocked by: #1477 (browser test runner) for every lesson whose spec uses calls, locals or struct fields in tests.