Answer: IBM Power4

Although the first dual-core processors the general public will readily recall are likely the early Athlon 64 X2 processors (released in 2005) or Pentium D processors (also released in 2005), the first commercially available dual-core processor was actually released by IBM in 2001.

Unlike the aforementioned offerings from AMD and Intel (which were released both for hobby computer builders and as part of mainstream desktop computers), the IBM chips were put into production directly in IBM RS/6000 and AS/400 computers (two lines that were comprised of high end servers, work stations, and super computers).

As such, unless you were a systems administrator around the turn of the millennium, there’s a good chance that you don’t recall any sort of buzz around the introduction of the first dual-core system (as significant as it was).