AMD Bulldozer CPUs were launched October 12, 2011. They were a complete re-design of earlier cores. The Bulldozer series were quickly dubbed "Faildozer" and they became an epic failure. This was partly due to the lack of multi-core support in software at the time and partly due to the fact that the first Bulldozer chips were slower than the Athlon II and Phenom II CPUs that came before it.
The chips are called the family 15h microarchitecture. It's predecessor was the 10h (K10) family microarchitecture so the jump from 10 to 15 made no sense. Perhaps it was because the miserable bulldozer failure was designed from scratch.
Faildozer CPUs ran hot and were sometimes called "space-heaters".
Before it's time
Part of the reason why Faildozer was such a failure really was a lack of multi-core support at the time. Bulldozers offered lots of cores with low per-core performance at a bargain. Intel had chips with less cores and much better single-core performance. If one chip runs a single thread fast and the other doens't but has more cores doing nothing then the faster single-threaded chip will win if the work-load is single-threaded.
Bulldozer chips run smoother now (since everthing's gone multi-core) than they did at launch. Vishera piledriver "black label" unleashed is quite fast with 6 or 8 cores, and you can keep away from the notorious intel processor bugs.