AMD's previous AthlonXP model, the Palomino (0.18 micron process) was nearing the end of its competitive life with the release of AthlonXP 2100+ in March 2002. With AMD's arch rival taking back the performance crown by an almost 800 MHz speed advantage, AMD was beginning to lag behind the performance curve in the minds of some consumers.

While the enthusiast community has long known that the Athlon core doesn't need the high clock speeds a Pentium 4 in order to do the same amount of work, the general public still remains largely fooled by the MHz-myth. Since it's speed that sells, and since the Pentium 4 has the performance crown, AMD was set to be overshadowed. The response to this has been the new AMD Ahthlon XP on the Thoroughbred core (0.13 micron process). The resulting die shrink should allow the AthlonXP to ramp up CPU speeds, and thus performance, even though it will still remain below that of the Intel Pentium 4.

So how does the T-Bred differ from the old Palomino core? Actually the T-Bred is basically the Palomino on a shrunken (0.13micron vs. 0.18micron) core!

AMD has refined the core a little now, that is why there are less transistors. 37.5 million on the Palomino and 37.2 million on the T-Bred. The actual CPU looks very much like the "Thunderbird" Athlon, with the rectangular shaped core and resistors on the top instead of on the bottom.

The core size is a tiny 80mm2 compared to the much larger 128mm2 for the Palomino, and 145mm2 of the P4 Northwood (131mm2 for 2.4GHz+). With the smaller manufacturing process, the T-Bred core doesn't require as much voltage, and more chips can be cut from the same size wafer. The T-Bred was originally introduced at speeds from XP1700+ to XP2200+ (1.43 GHz - 1.8 GHz) and the chart below shows a little diagram explaining the different voltages and thermal outputs.

As we can see, the AthlonXP1700+ to 1900+'s use a voltage of 1.5V, while the XP2000+ and 2100+ use 1.6V and the current flagship XP2200+ needs 1.65V.

The T-Bred is still quite a "toasty" processor, it doesn't give out as much heat as the 1.4 GHz Athlon or XP2100+ (Palomino) but it comes pretty close.