as Barton were replaced in September 2003 by the Athlon 64 family, which featured an on-chip memory controller and a new HyperTransport bus. Notably, the 2500+ Barton with 11× multiplier was effectively identical to the 3200+ part other than the FSB speed it was binned for, meaning that seamless overclocking was possible more often than not. Early Thortons could be restored to the full Barton specification with the enabling of the other half of the L2 cache from a slight CPU surface modification, but the result was not always reliable. Specifications Barton (130 nm) L1-cache: 64 + 64 KB (data + instructions) L2-cache: 512 KB, full speed MMX, 3DNow!, SSE Socket A (EV6) Front-side bus: 166/200 MHz (333/400 MT/s) Vcore: 1.65 V First release: February 10, 2003 Clock rate: 1833–2333 MHz (2500+ to 3200+) 133 MHz FSB: 1867–2133 MHz (2500+ to 2800+); uncommon 166 MHz FSB: 1833–2333 MHz (2500+ to 3200+) 200 MHz FSB: 2100, 2200 MHz (3000+, 3200+) Thorton (130 nm) L1-cache: 64 + 64 KB (Data + Instructions) L2-cache: 256 KB, full speed MMX, 3DNow!, SSE Socket A (EV6) Front-side bus: 133/166/200 MHz (266/333/400 MT/s) Vcore: 1.50–1.65 V First release: September 2003 Clock rate: 1667–2200 MHz (2000+ to 3100+) 133 MHz FSB: 1600–2133 MHz (2000+ to 2600+) 166 MHz FSB: 2083 MHz (2600+) 200 MHz FSB: 2200 MHz (3100+) Mobile Athlon XP The Palomino core debuted in the mobile market before the PC market, where it was branded as Mobile Athlon 4 with the codename "Corvette". It distinctively used a ceramic interposer much like the Thunderbird instead of the organic pin grid array package used on all later Palomino processors. In November 2001, AMD released a 1.2 GHz Athlon 4 and a 950 MHz Duron. The Mobile Athlon 4 processors included the PowerNow! function, which controlled a laptop's "level of processor performance by dynamically adjusting its operating frequency and voltage according to the task at hand", thus extending "battery life by reducing processor power when it isn't needed by applications". Duron chips also included PowerNow! In 2002, AMD released a version of PowerNow! called Cool'n'Quiet, implemented on the Athlon XP but only adjusting clock speed instead of voltage. In 2002 the Athlon XP-M (Mobile Athlon XP) replaced the Mobile Athlon 4 using the newer Thoroughbred core, with Barton cores for full-size notebooks. The Athlon XP-M was also offered in a compact microPGA socket 563 version. Mobile XPs were