The AMD K9 represents a microarchitecture by AMD designed to replace the K8 processors, featuring dual-core processing.
[1] At one point, K9 was the Greyhound project at AMD, and was worked on by the K7 design team beginning in early 2001, with tape-out revision A0 scheduled for 2003.
The existence of a massively parallel CPU design concept for heavily multi threaded applications has also been revealed, as a planned successor to K8.
This was reportedly canceled in the conceptualization phase, after about 6 months' work.
[2] At one time K9 was the internal codename for the dual-core AMD64 processors as the brand Athlon 64 X2;[3][4] however, AMD has distanced itself from the old K series naming convention, and now seeks to talk about a portfolio of products tailored to different markets.