Pfunk, the Bartons also have 512 kB of L2 cache, vs 256 kB in the Throughbred.
When you hear names like Barton, Palomino, Throughbred, Thunderbird, Clawhammer, Spitfire, Northwood, Willamette, Prescott, etc associated with CPUs what you are hearing is the internal company names for different designs.
In the Athlon XP line there are Palominos, Throughbred A & B, and Bartons.