AMD Athlon 64 2800+
The Athlon 64 2800+ on socket 754 was available in two versions: one (like this) with a New Castle core and one with a Clawhammer core. Clawhammer is the core on which the first Athlon 64's were based. New Castle followed quickly after and had one major difference: it 'only' had 512KB L2 in it's chip. Clawhammer featured 1MB L2.
The 2800+ with the Clawhammer also has 512KB like the New Castle. There is no difference in performance but there is a difference in the manufacturing process: the Clawhammer has a bigger 'die' (CPU-core) because of the 1MB L2 in total so AMD can slice less CPU's from a wafer compared to CPU's that are manufactured with 512KB L2 cache. On the other hand: 1MB Clawhammer CPU's that have defects in one part of the L2-cache can be configured to disable half the L2-cache. All the 1MB CPU's that didn't validate for 1MB can still be sold as 512KB part rather than being thrown away.
The 2800+ is the lowest clocked (and rated) S754 production CPU made by AMD.