A four CPU processor released by AMD Inc. in the year 2007, in the Agena core variant, and in the year 2009, with the Deneb core variant.
The Agena variant of the Phenom processor had a defect (errata) which made all of these chips somewhat slower than AMD's high range dual core chips and substantially slower than its competition's quad core chips. This hurt AMD's reputation and caused it to lose prestige and footing in the market.
The Deneb variant has no errata issues and is fairly competitive with other quad core processors by competing manufacturers.
The benchmarks published on most computer enthusiast websites confirm that the Phenom 9500 is actually slower in most applications than the Athlon X2 6000.