Depends. Specifically, there were three known versions of the Socket 478 P4 2.8 produced:
- P4 2.8B (533 MHz FSB, Northwood core - 512K L2 cache)
- P4 2.8C (800 MHz FSB, HT, Northwood core - 512K L2 cache)
- P4 2.8E (800 MHz FSB, HT, Prescott core - 1MB L2 cache)
The Athlon XP 2800+ was produced in both 266 (rare) and 333 MHz FSB variants, and the latter can easily outperform a P4 2.8B, but chances, are the HT-enabled P4s (the "C" and "E" variants) are still faster. As the Athlon XP increased in frequency, its limitations began to show. Just to give you an idea, an Athlon XP 3200+ (400 MHz FSB) can hold itself against a P4 3.06 HT (533 MHz FSB), but is only equivalent to a P4 2.6-2.8C (800 MHz FSB) in most games in terms of performance.