AMD Duron processor is a low-cost CPU based on the K7 architecture. The first generation of Duron processors used Spitfire core, which is similar to the Athlon Thunderbird core with the exception of L2 cache - the Duron had 64 KB L2 cache while the Athlon had 256 KB cache. Having larger L1 cache, faster bus speed and more powerful FPU unit, the Duron Spitfire processors significantly outperformed their competitors - Intel Celeron processors with 66 Mhz FSB. Even after the bus speed on Celeron processors was increased to 100 MHz, they were still lagging behind the Duron CPUs.
The Spitfire core Durons were produced in speeds up to 950 MHz. Faster AMD Duron processors used a Morgan core. Like the Spitfire core is similar to the Thunderbird core, the Morgan core takes most of the features from the Athlon Palomino core. The core was tweaked for greater performance by implementing a full set of SSE instructions, adding a data prefetch mechanism and increasing the size of the Translation Look-aside Buffer.
The next Duron core - Applebred - was used in the last three processors from the Duron family. In these processors the bus speed was increased to 266 MHz, and the core voltage was reduced to 1.5V. The Applebred core was the last Duron core - the Duron CPU family was phased out in favor of new AMD Sempron family.