ADR-0003/0014: generalize "router mesh" to "NOC"
NOC topology is an implementation choice (mesh, ring, crossbar, etc.). ADR-0017 covers the current 2D mesh choice; ADRs at the system-level shouldn't bind to that specific implementation. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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@@ -44,15 +44,15 @@ Each PE contains the following logical components.
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**PE_DMA**
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- Handles memory transfers between PE_TCM and external memory domains.
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- PE_DMA connects to the NOC router mesh at the CUBE level (ADR-0019):
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- All destinations (HBM, shared SRAM, inter-cube UCIe) are reached via the router mesh
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- Local HBM access: PE_DMA → local router → hbm_ctrl (switching overhead only)
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- Remote/shared: PE_DMA → local router → (mesh hops) → destination
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- PE_DMA connects to the cube-level NOC (on-die fabric):
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- All destinations (HBM, shared SRAM, inter-cube UCIe) are reached via the NOC
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- Local HBM access: PE_DMA → NOC → hbm_ctrl (minimal hop)
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- Remote/shared: PE_DMA → NOC → (fabric hops) → destination
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- Supported directions include:
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- HBM → PE_TCM (via router mesh)
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- PE_TCM → HBM (via router mesh)
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- PE_TCM → shared SRAM (via router mesh)
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- PE_TCM → other memory domains (via router mesh, if supported by topology)
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- HBM → PE_TCM (via NOC)
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- PE_TCM → HBM (via NOC)
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- PE_TCM → shared SRAM (via NOC)
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- PE_TCM → other memory domains (via NOC, if supported by topology)
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**PE_GEMM**
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@@ -252,7 +252,7 @@ Compute operations use a TCM-centric dataflow model.
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**Input path (HBM)**
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```text
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HBM → router mesh → PE_DMA (DMA_READ) → PE_TCM
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HBM → NOC → PE_DMA (DMA_READ) → PE_TCM
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```
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**Input path (shared SRAM)**
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@@ -269,14 +269,14 @@ Compute engines read input tensors from PE_TCM.
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PE_TCM → GEMM / MATH
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```
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Weights for GEMM may optionally stream directly from HBM (via router mesh).
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Weights for GEMM may optionally stream directly from HBM (via NOC).
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**Output path (HBM)**
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Compute results are written to PE_TCM, then DMA writes to HBM.
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```text
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PE_TCM → PE_DMA (DMA_WRITE) → router mesh → HBM
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PE_TCM → PE_DMA (DMA_WRITE) → NOC → HBM
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```
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**Output path (shared SRAM)**
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@@ -348,9 +348,9 @@ PE instances are derived from `cube.pe_layout`.
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External connectivity such as:
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- PE_DMA → router mesh → HBM (data path, ADR-0019)
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- PE_DMA → router mesh → shared SRAM, inter-cube UCIe (non-HBM data path)
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- router mesh → PE_CPU (command path from M_CPU)
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- PE_DMA → NOC → HBM (data path)
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- PE_DMA → NOC → shared SRAM, inter-cube UCIe (non-HBM data path)
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- NOC → PE_CPU (command path from M_CPU)
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is modeled at the CUBE level (see ADR-0003 D3).
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