The first Sempron CPUs were based on the
Athlon XP architecture using the
Thoroughbred or
Thorton core. These models were equipped with the
Socket A interface, 256
KiB L2 cache and 166 MHz
Front side bus (FSB 333). Thoroughbred cores natively had 256 KiB L2 cache, but Thortons had 512 KiB L2 cache, half of which was disabled and could sometimes be reactivated with a slight physical modification to the chip. Later, AMD introduced the Sempron 3000+ CPU, based on the
Barton core with 512 KiB L2 cache. From a hardware and user standpoint, the Socket A Sempron CPUs were essentially identical to Athlon XP desktop CPUs with a new brand name. The second generation (
Paris/
Palermo core) was based on the architecture of the
Socket 754 Athlon 64. Some differences from Athlon 64 processors include a reduced cache size (either 128 or 256 KiB L2), and the absence of AMD64 support in earlier models. Apart from these differences, the Socket 754 Sempron CPUs share most features with the more powerful Athlon 64, including an integrated (on-die)
memory controller, the
HyperTransport link, and AMD's "
NX bit" feature. In the second half of 2005, AMD added 64-bit support (
AMD64) to the Sempron line. Some journalists (but not AMD) often refer to this revision of chips as "Sempron 64" to distinguish it from the previous revision. AMD's intent in releasing 64-bit entry-level processors was to extend the market for 64-bit processors, which at the time of Sempron 64's first release, was a
niche market. In 2006, AMD announced the
Socket AM2 and
Socket S1 line of Sempron processors. These are functionally equivalent to the previous generation, except they have a dual-channel
DDR2 SDRAM memory controller which replaces the single-channel
DDR SDRAM version. The
TDP of the standard version remains at 62 W (watts), while the new "Energy Efficient Small Form Factor" version has a reduced 35 W TDP. The Socket AM2 version also does not require a minimum voltage of 1.1 volts to operate, whereas all socket 754 Semprons with Cool'n'Quiet did. In 2006, AMD was selling both Socket 754 and Socket AM2 Sempron CPUs concurrently. In the middle of 2007 AMD appears to have dropped the 754 line and is shipping AM2 and S1 Semprons. == Models for Socket A (Socket 462) ==