docs: a slower clock can't fix the seed-lottery — pipelining is the fix (Refs #1764)

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Investigated and ruled out the intuitive "run the deep shared-core path on a slower clock" remedy for the on-silicon seed-lottery marginality, on two independent grounds:

• Not buildable on openXC7. A fabric-counter divided clock needs a clock buffer, and nextpnr-xilinx cannot place one driven from fabric — both BUFG and BUFR fed by a divider bit fail with "Unable to find legal placement" (7-series clock-buffer inputs come from clock-capable pins / the CMT, not general routing). Only an MMCM/PLL could synthesize a real divided clock.
• Wouldn't help even if built. A divided clock with the same microcode settle gives the same real settle window (~µs) as the working /N clock-enable, and more settle does not cure the glitch — silicon behaviour is non-monotonic in settle (/128 glitched worse than /64, cycle 93). The fault is a placement hazard, not a settle shortage.

Also re-confirmed create_clock on clk_p does not propagate through IBUFDS (internal net defaults to a loose 12 MHz target and always "passes", so --timing-allow-fail was effectively a no-op).

Conclusion (re-prioritises the roadmap): the one viable structural fix is to PIPELINE the shared GftSmul/GftSadd (a spec-level on_clock pipelined multiply/add), which breaks the deep combinational hazard and is the prerequisite for on-silicon training beyond XOR (seed-search runs out at 62 steps).

Docs-only; no code or gate changes. Refs #1764

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PR Dashboard

Generated at: 2026-08-07 19:29:25 UTC

• docs: a slower clock can't fix the seed-lottery — pipelining is the fix (Refs #1764) #1897 docs: a slower clock can't fix the seed-lottery — pipelining is the fix (Refs #1764) | Created: 2026-08-07 | Updated: 2026-08-07 | 11 failing / 15 total
• chore: civilian mesh positioning — drop drone wording (bpsk.t27) #1874 chore: civilian mesh positioning — drop drone wording (bpsk.t27) | Created: 2026-08-07 | Updated: 2026-08-07 | 2 failing / 25 total
• feat(igla): Wave Loop 897 — module-scope [613][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1858 feat(igla): Wave Loop 897 — module-scope [613][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 1 failing / 3 total
• feat(igla): Wave Loop 896 — module-scope [611][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1856 feat(igla): Wave Loop 896 — module-scope [611][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 1 failing / 3 total
• feat(igla): Wave Loop 895 — module-scope [609][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1854 feat(igla): Wave Loop 895 — module-scope [609][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 1 failing / 3 total
• feat(igla): Wave Loop 894 — module-scope [607][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1852 feat(igla): Wave Loop 894 — module-scope [607][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 1 failing / 3 total
• feat(igla): Wave Loop 893 — module-scope [605][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1850 feat(igla): Wave Loop 893 — module-scope [605][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 1 failing / 3 total
• feat(igla): Wave Loop 892 — module-scope [603][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1847 feat(igla): Wave Loop 892 — module-scope [603][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 1 failing / 3 total
• feat(igla): Wave Loop 891 — module-scope [601][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1844 feat(igla): Wave Loop 891 — module-scope [601][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 0 failing / 4 total
• feat(igla): Wave Loop 890 — module-scope [599][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1842 feat(igla): Wave Loop 890 — module-scope [599][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-07 | Updated: 2026-08-07 | 0 failing / 4 total
• feat(igla): Wave Loop 883 — module-scope [585][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1815 feat(igla): Wave Loop 883 — module-scope [585][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-06 | Updated: 2026-08-06 | 0 failing / 1 total
• feat(igla): Wave Loop 882 — module-scope [583][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1813 feat(igla): Wave Loop 882 — module-scope [583][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-06 | Updated: 2026-08-06 | 0 failing / 12 total
• feat(igla): Wave Loop 881 — module-scope [581][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1810 feat(igla): Wave Loop 881 — module-scope [581][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes | Created: 2026-08-06 | Updated: 2026-08-06 | 0 failing / 12 total

Summary

Status	Count
Total Open PRs	13
PRs with Failing Checks	1
PRs with All Checks Green	12
READY	5
FAILING	1
PENDING	0

Seal Status

• ⚠️ STALE -- sha256(compiler.rs)=f74459fc23c3 != manifest seal=87e5cbd3ad94.
  The committed NMSE numbers were certified against an older compiler.rs.
  Run scripts/reseal-check.sh locally for the two-step reseal command (advisory; not a merge gate).