Prediction accuracy
2-bit vs. 1-bit
- Significant gain (approx. 92% vs. 85% for f-p in Spec89 benchmarks, 90% vs. 80% in gcc but about 88% for both in compress)
Table size and organization
- The larger the table, the better (in general) but seems to max out at 512 to 1K entries
- Larger associativity also improves accuracy (in general)
- Why “in general” and not always? Some time “aliasing” is beneficial