TechPowerUp reports the ACC (Advanced Clock Calibration) trick in the BIOS of motherboards with the AMD SB710 or SB750 southbridge also works on the Sempron 140 processor. By activating this feature in the BIOS, the disabled second core of the chip will be unlocked, turning it into an Athlon II X2.
The trick requires a motherboard with AMD SB710 or SB750 southbridge that supports the Advanced Clock Calibration feature. Not all motherboards, however, support this mod. By simply enabling the feature in the BIOS setup program, the system will be able to address both processor cores, with the complete feature-set of Athlon II X2. The staff behind the feat over at Thai techsite VModTech tested for the unlocked core's stability with much success. At 3.71 GHz (13.5 x 275 MHz @ 1.536 V), the processor stood SuperPi, WPrime, and WinRAR bandwidth tests. Validation can be found here. At around $40, here's the cheapest ticket to a dual-core processor that looks $80 Intel processors in the eye.