AMD Athlon 64 3500+
The 3500+ was a good performing product for quite a while. The first 3500+ with Clawhammer core (130nm) was announced half-way 2004. The first Venice (90nm) core was introduced in April 2005 and this CPU was made in the 46th week of 2005. Quite a bit later and the first dual-core processors were around by then.