Do the optima of the fan-in sweep move when columns and MAC lanes go past 8?

What it found

The F-F-4 quantised-MLP comparison of chip-systolic-fanin with wider grids (C up to 16, P up to 32, F = 16 and 32), all 12 array configurations matched to an integer NumPy reference in Icarus Verilog and scored with Yosys. A negative result: the earlier optima were at the sweep edge and move inward (best array 2×8, best MAC engine P = 16 at F = 32), but the best array still costs 1.25× (F = 16) and 1.20× (F = 32) the cells×cycles per vector of the best MAC engine. Stylised: one network family, one seed, generic-gate counts, no layout.

A figure from its own output

Paper, code and results

• README and method
• Experiments and results
• Code
• Tests

More in LLM chip design loops

• Does the array/MAC-engine gap change when the hidden width is fixed at 8 and only the input fan-in grows?Fixes the hidden width at 8 and sweeps the input fan-in F = 8, 16, 32: the best MAC engine still beats the best systolic array, by 1.35x, 1.22x and 1.20x in cells-times-cycles per vector (negative, stylised, generic-gate counts).
• Which MAC-lane count is best for a tiny quantised MLP if every P from 1 to 20 is built and checked?Builds and RTL-checks every MAC-lane count P = 1 to 20 on the F-16-4 network (F = 16, 32): the best P is 8 and 16, no non-power-of-two wins, and P above 16 only adds cells (stylised, generic-gate counts).
• Does the MAC-engine lead survive a wider hidden layer (H = 16) and more MAC lanes?Widens the hidden layer to 16 (F = 16, 32) and lets the MAC engine reach P = 16: the best MAC engine still beats the best systolic array, by 1.30x and 1.27x in cells-times-cycles per vector, and at F = 32 its best lane count is again the largest tried (negative, stylised, generic-gate counts).
• Does the MAC-engine lead survive MAC lanes up to P = 32 and arrays up to R = 4?Extends the hidden-16 comparison to MAC lanes up to P = 32 and arrays up to 4x8 with every design simulated: the best MAC engine still wins, by 1.30x and 1.28x in cells-times-cycles per vector; P = 32 adds no cycles over P = 16 (negative, stylised, generic-gate counts).
• Does the MAC engine beat a systolic array under every ABC script, not just Yosys's default?Re-scores chip-systolic-p32's 20 designs under five ABC scripts: the best MAC engine beats the best systolic array in all ten F x script cases, by 1.28x to 1.60x (negative for arrays, stylised, generic-gate counts).
• Is P = 32 being smaller than P = 16 at equal cycles a real effect or a synthesis artefact?Re-synthesises the 16- and 32-lane MAC engines (same cycles) with three seeds and three Yosys flows: the sign of the cell-count gap depends on the flow, with swings of 1-10%, so chip-systolic-p32's 0.7% ranking is not reliable (artefact-sensitive, stylised, generic-gate counts).

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.