Definition
Coarse-Grained Hardware Multi-Threading
Coarse-grained hardware multi-threading switches between threads only on costly stalls, typically L2 or L3 cache misses.
The pipeline drains before switching, so a thread that is running without stalls executes continuously.
Trade-off
- Advantage: does not slow down threads that are not stalled.
- Disadvantage: cannot hide short stalls — the thread switch overhead (pipeline drain and fill) is too high to justify switching for a few cycles.
Because it only helps with long-latency events, it is the simplest form of hardware multi-threading.