Does a wider fan-in let a small systolic array catch a MAC-lane engine on a tiny quantised MLP?

What it found

The small output-stationary arrays of chip-systolic-small on an F-F-4 quantised MLP with F = 8, 16 and 32 (4-bit weights), all 12 array configurations matched to an integer NumPy reference and the cycle formula in Icarus Verilog, scored with Yosys against MAC-lane engines. A negative result: the best array costs 1.36×, 1.25× and 1.26× the cells×cycles per vector of the best MAC engine at F = 8, 16 and 32, so the gap narrows but does not close. Stylised: one seed, gate counts rather than area, no clock, power or layout, and some optima at the edge of the sweep.

A figure from its own output

Paper, code and results

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More in LLM chip design loops

• Do the optima of the fan-in sweep move when columns and MAC lanes go past 8?Extends the fan-in sweep past its edges (C = 16, P = 32): the optima move inward and the best array still costs 1.25x (F = 16) and 1.20x (F = 32) the cells-times-cycles per vector of the best MAC engine (negative, stylised, generic-gate counts).
• 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).

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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.