Released in August 2002 as successor to the Thoroughbred 'A'. It was still 130nm but refined and optimized to reach higher clock-frequencies. AMD added a 9th layer ('A' had 8 layers) to improve electrical conduction between parts of the CPU. This greatly increased stability at higher clocks.
In early 2003 AMD perfected the 130nm production process. AMD had good yields per wafer that caused AMD to sell high-quality chips rated at low speeds to satisfy demands on budget CPU's. It didn't take long for people to find out that the cheap 1700+ and 1800+ CPU's could reach clock-frequencies equal or exceeding those of AMD's high-end CPU's. Back in the day I bought a 60 Euro XP1700+ that ran at 2,5GHz for years with ease. Some even exceeded 3GHz using LN2 (Hydrogen) cooling!
The Thoroughbred 'B' got AMD back on the track after the Palomino (180nm) was stretched to it's limits and Thoroughbred 'A' didn't meet expectations.
Personally I loved this chip in combination with the nForce2 chipset. Easy to overclock, dead stable and by setting latencies right (and tight using proper memory chips), the feeling of the system was really snappy. And, of course the excellent price/performance ratio.