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>
This commit is contained in:
2026-05-14 23:23:46 -07:00
parent c9bd5387ac
commit 32b29a1e5c
2 changed files with 21 additions and 19 deletions
@@ -44,15 +44,15 @@ Each PE contains the following logical components.
**PE_DMA**
- Handles memory transfers between PE_TCM and external memory domains.
- PE_DMA connects to the NOC router mesh at the CUBE level (ADR-0019):
- All destinations (HBM, shared SRAM, inter-cube UCIe) are reached via the router mesh
- Local HBM access: PE_DMA → local router → hbm_ctrl (switching overhead only)
- Remote/shared: PE_DMA → local router → (mesh hops) → destination
- PE_DMA connects to the cube-level NOC (on-die fabric):
- All destinations (HBM, shared SRAM, inter-cube UCIe) are reached via the NOC
- Local HBM access: PE_DMA → NOC → hbm_ctrl (minimal hop)
- Remote/shared: PE_DMA → NOC → (fabric hops) → destination
- Supported directions include:
- HBM → PE_TCM (via router mesh)
- PE_TCM → HBM (via router mesh)
- PE_TCM → shared SRAM (via router mesh)
- PE_TCM → other memory domains (via router mesh, if supported by topology)
- HBM → PE_TCM (via NOC)
- PE_TCM → HBM (via NOC)
- PE_TCM → shared SRAM (via NOC)
- PE_TCM → other memory domains (via NOC, if supported by topology)
**PE_GEMM**
@@ -252,7 +252,7 @@ Compute operations use a TCM-centric dataflow model.
**Input path (HBM)**
```text
HBM → router mesh → PE_DMA (DMA_READ) → PE_TCM
HBM → NOC → PE_DMA (DMA_READ) → PE_TCM
```
**Input path (shared SRAM)**
@@ -269,14 +269,14 @@ Compute engines read input tensors from PE_TCM.
PE_TCM → GEMM / MATH
```
Weights for GEMM may optionally stream directly from HBM (via router mesh).
Weights for GEMM may optionally stream directly from HBM (via NOC).
**Output path (HBM)**
Compute results are written to PE_TCM, then DMA writes to HBM.
```text
PE_TCM → PE_DMA (DMA_WRITE) → router mesh → HBM
PE_TCM → PE_DMA (DMA_WRITE) → NOC → HBM
```
**Output path (shared SRAM)**
@@ -348,9 +348,9 @@ PE instances are derived from `cube.pe_layout`.
External connectivity such as:
- PE_DMA → router mesh → HBM (data path, ADR-0019)
- PE_DMA → router mesh → shared SRAM, inter-cube UCIe (non-HBM data path)
- router mesh → PE_CPU (command path from M_CPU)
- PE_DMA → NOC → HBM (data path)
- PE_DMA → NOC → shared SRAM, inter-cube UCIe (non-HBM data path)
- NOC → PE_CPU (command path from M_CPU)
is modeled at the CUBE level (see ADR-0003 D3).