As we briefly mentioned at the start of this article, the Athlon XP 2100+ is a generic speed bump in the simplest of terms. The CPU is architecturally identical to all other Palominos and has power characteristics very similar to the Athlon XP 2000+. The reason being that there's only a 67MHz difference between the 2100+ and the 2000+ (1.73GHz vs. 1.67GHz).
With only a 4% difference in clock speed you can't expect to see much of a tangible performance difference between the 2100+ and the 2000+. In fact, the only visible difference between the two chips is that AMD has gone to a different dye color for the packaging substrate.

From now on, all Athlon XPs will feature this green substrate which is reminiscent of the FC-PGA Pentium III CPUs. This change in substrate dye won't change performance at all, but it's always nice to see something different in our CPU drawers.