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ywkang a796c1d2f7 ADR: bilingual structure — EN canonical in adr/, KO mirror in adr-ko/

Establish English as the canonical ADR language with Korean translations
held in a parallel docs/adr-ko/ tree as derived artifacts (1:1 mirror).
Promotion from adr-proposed/ to adr/ now writes English to adr/ and the
Korean to adr-ko/; bidirectional sync rule documented in CLAUDE.md.

- Migrate 30 ADRs in docs/adr/: 28 Korean-only translated to English,
  2 bilingual pairs (ADR-0020, ADR-0023) consolidated (.en.md suffix
  dropped). ADR-0023 EN regenerated against KO source which had newer
  HW Realization Notes (D16-D23) section.
- docs/adr-history/ left frozen by design (transitional state).
- CLAUDE.md (Part 2): update ADR Lifecycle for 4-folder layout, mark
  docs/adr-ko/ as a Derived Artifact, add ADR Translation Discipline
  section covering bidirectional sync, conflict resolution (EN wins),
  and proposed-language freedom.
- tools/verify_adr_lang_pairs.py: new verification tool checking pair
  completeness, filename mirroring, ADR-ID match, Status byte-equality.
  Pre-commit hook intentionally not added; run on demand or in CI.
- tests/test_verify_adr_lang_pairs.py: 11 cases including CRLF/LF
  normalization, em-dash title separator, underscore-slug edge case.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-20 01:38:44 -07:00

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ADR-0004: Memory Semantics & Local-HBM Bandwidth Guarantee

Status

Accepted

Context

Accurately modeling PE↔HBM behavior is essential for kernel latency estimation. Each PE has a notion of “local HBM” that must guarantee full HBM bandwidth, independent of intervening on-die fabric bandwidth.

Decision

D1. Local HBM definition

Each PE is assigned a logically defined “local HBM” region.
Local HBM corresponds to the pseudo-channel subset directly attached to that PE’s router in the NOC mesh (ADR-0017 D4).
The path is: PE_DMA → local router → HBM_CTRL (switching overhead only, 0 mesh hops).
The mapping (HBM pseudo-channels → PE local regions) is derived from topology configuration.

D2. Local HBM bandwidth guarantee contract

Accesses from a PE to its local HBM MUST guarantee full effective HBM read/write bandwidth independent of intervening fabric bandwidth limits.
Effective HBM bandwidth = spec bandwidth x efficiency factor. The efficiency factor (configured via hbm_ctrl.attrs.efficiency, default 0.8) models real-world DRAM inefficiencies (refresh cycles, bank conflicts, page misses). For example: 256 GB/s spec x 0.8 = 204.8 GB/s effective.
The topology builder applies the efficiency factor to router-to-hbm edge bandwidth at graph construction time, so all downstream routing and latency computation uses the effective value.
This guarantee is modeled by:
- a dedicated logical path and/or service model that enforces HBM BW at the PE-local-HBM interaction point,
- while still incurring non-zero latency along explicitly modeled components.
HBM CTRL internal modeling (PC striping, cut-through, scheduling fidelity) is consolidated in ADR-0033 (Latency Model: Assumptions and Known Simplifications). The aggregate BW guarantee here remains the contract; ADR-0033 documents how the per-PC model realizes it and which scheduler effects are intentionally simplified.

D3. Remote PE HBM semantics (intra-cube)

A PE that accesses another PE's local HBM traverses the NOC:
- PE_DMA → NOC → (fabric hops) → target PE's NOC port → HBM_CTRL
NOC bandwidth and hop count may limit remote HBM access relative to local access.

D4. Non-local HBM semantics (inter-cube / inter-SIP)

Accesses from a PE to HBM in a different cube or SIP MAY be limited by:
- NOC bandwidth within the cube,
- inter-cube UCIe links,
- inter-SIP fabric (PCIe/UAL).
These paths MUST be explicit and traceable.

D5. Shared SRAM semantics

Each CUBE contains a shared SRAM accessible by all PEs in that CUBE.
Access path: PE_DMA → NOC → shared SRAM.
Shared SRAM bandwidth is limited by the NOC↔SRAM link bandwidth.
Shared SRAM is not part of the HBM address space; it is a separate memory domain.

Verification Notes

Tests should cover:

local-HBM case: BW matches HBM BW regardless of fabric BW parameter
remote PE HBM case: latency includes mesh hop traversal
non-local cases (inter-cube/inter-SIP): BW/latency respond to fabric/link parameters
shared SRAM case: access via NOC with correct BW

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