The Thunderbird core of AMD Athlon CPU. Available in speeds ranging from 650 MHz to 1.4 GHz. Most are Socket A CPUs, though some were made in Slot A versions for backward compatability. All are made on a 0.18 process, with 256k of L2 cache, and 64K of L1.
Athlon Thunderbirds (especially the higher models like the 1.33 and the 1.4) became known for their immense heat output, especially when overclocked. Since most heatsinks at the time still used 60mm fans, a Delta 38 was often used to cool them off, despite it sounding like a hair dryer. A Tbird 1.4 pumps out about 75 watts of heat at stock speed and voltacge (1.75), and it wasn't untill the likes of the AX-7 came along that they became more accessable to overclocking.
The record for Thunderbird overclocking was, I believe, set by a man in Japan who used LN2 (Liquid Nitrogen) to chill a 1GHz AXIA Thunderbird, which he then overclocked to some 2 GHz.
"My Barton 2500 died, so I bought a cheap Tbird to keep my system running."