AHB vs AXI Comparison
Understanding why we moved from Shared Bus (AHB) to Crossbar/NoC (AXI).
1. Architecture: Shared vs Point-to-Point
AHB (Shared Bus): Only ONE Master can grant the bus at a time. The Arbiter decides. If Master A is writing, Master B must wait. Good for simple, low-latency control logic.
AXI (Point-to-Point / Crossbar): Handles 5 independent channels. Multiple Masters can talk to Multiple Slaves simultaneously. Supports out-of-order return. Optimized for High Bandwidth (Video/DDR).
2. Feature Comparison
| Feature | AHB | AXI |
|---|---|---|
| Channels | Shared (Addr, WData, RData phases) | 5 Dedicated (AR, AW, W, R, B) |
| Duplex | Half Duplex (Read OR Write) | Full Duplex (Read AND Write same time) |
| Phase | Pipelined (Addr Phase N, Data Phase N+1) | Decoupled (Addr/Data independent) |
| Burst | Fixed length needed early (often) | Supports streaming/indefinite |