multi die design
**Multi-Die and Chiplet Design Methodology** is the **EDA and architectural approach to designing systems composed of multiple smaller silicon dies (chiplets) connected through advanced packaging rather than a single monolithic die** — enabling the combination of different process nodes, IP blocks from different vendors, and die sizes optimized for yield, where the design methodology requires new tools for die-to-die interface design, system-level floorplanning, cross-die timing closure, and thermal/power co-analysis that traditional single-die EDA flows do not provide.
**Why Multi-Die/Chiplet**
- Monolithic die: Larger die → exponentially lower yield → cost explodes above ~400mm².
- Chiplet: Four 100mm² dies at 90% yield each = 65% system yield vs. 400mm² at ~30% yield.
- Heterogeneous nodes: CPU on 3nm, I/O on 12nm, memory on dedicated → each optimized.
- Mix and match: Reuse proven chiplets across products → reduce design effort.
- Examples: AMD EPYC (CCD + IOD), Intel Meteor Lake (compute + SOC + GFX tiles), Apple M-series.
**Multi-Die Design Flow**
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**Die-to-Die Interface Design**
| Interface Standard | Bandwidth | Reach | Latency | Energy |
|-------------------|-----------|-------|---------|--------|
| UCIe (Universal Chiplet Interconnect Express) | 32 GT/s/lane | <2mm | ~2ns | 0.5 pJ/bit |
| BoW (Bunch of Wires) | 2-8 GT/s/lane | <10mm | ~3-5ns | 0.1-0.5 pJ/bit |
| AIB (Advanced Interface Bus) | 2-4 GT/s/lane | <5mm | ~5ns | 0.5-1 pJ/bit |
| HBM PHY | 3.2 GT/s/pin | <5mm | ~10ns | 1-3 pJ/bit |
| Custom SerDes (long reach) | 56-112 GT/s/lane | 10mm+ | ~10ns | 5-15 pJ/bit |
**EDA Tool Challenges**
| Challenge | Single Die | Multi-Die |
|-----------|-----------|----------|
| Timing closure | One die, one PVT | Cross-die + package + PVT per die |
| Power analysis | One power grid | Multiple power domains, package PDN |
| Thermal analysis | One die | Die-to-die heat coupling, stacked thermal |
| Verification | One GDSII | Multiple GDSII + package + interposer |
| Floor planning | 2D | 2.5D/3D + package + interposer routing |
**System-Level Timing**
- Die 1 output → D2D TX → bump → interposer → bump → D2D RX → Die 2 input.
- Total latency: ~2-10ns depending on interface (vs. ~0.1-0.5ns for on-die paths).
- Timing constraint: Must account for die-to-die latency + jitter + skew.
- Thermal variation: Each die at different temperature → different delay → cross-die OCV.
**Emerging EDA Capabilities**
| Capability | Tool/Vendor | Purpose |
|-----------|------------|--------|
| 3D IC Compiler | Synopsys 3DIC | Multi-die floorplan + routing |
| Integrity 3D-IC | Cadence | Cross-die parasitic + timing |
| Multi-die power integrity | Ansys RedHawk-SC | Cross-die IR drop + EM |
| Package co-design | Siemens Xpedition | Package substrate routing |
Multi-die chiplet design methodology is **the architectural paradigm that is replacing monolithic scaling as the primary path to more powerful chips** — by decomposing complex systems into composable chiplets that can be independently designed, fabricated at optimal nodes, and combined through advanced packaging, the semiconductor industry is transcending the yield and cost limitations of monolithic die, making chiplet design competency the new essential skill for every chip architect and physical design team.