The Sempron brand is synonymous with the bottom of the market, dawdling beneath AMD's Athlon range for more than five years. It's still a weakling, but new versions bear little resemblance to the original.
Although today's Sempron remains resolutely single-core - the only such CPU this month - it's based on the same architecture as the Athlon II range.
Indeed, internally it's effectively an Athlon II X2 with one core disabled, using the same 45nm AM3 architecture and featuring 1MB of L2 cache. As you'd expect, though, it draws less power than its dual-core cousins, with its 45W thermal design power lower than anything else on test. Like all AM3 parts, it will also work in an older Socket AM2+ motherboard.
While the older LE-1250 is still around and priced at just $41, it's the newer 2.7GHz Sempron 140 that has potential. With a benchmark score of 1.04 and a street price of around $46, it's perfect for a small, quiet media PC, or a cheap system to outdo a nettop.
Of course, while it holds its own in applications such as Word, it struggles with anything multithreaded - in graphical applications, it took almost twice as long as the slowest dual-core Athlon II, and even the 2.4GHz dual-core Celeron beat it.
Tantalisingly, on some motherboards it's possible to unlock the Sempron's dormant second core. If it works, you get a cheap equivalent to an Athlon II X2, but it's a hit-and-miss proposition - in some units the second core may be faulty, and you'll void your warranty if you even attempt to enable it.
But if you're willing to risk it, a simple web search should reveal the type of board you need and the BIOS setting you need to adjust.
Hacking aside, the Sempron 140 isn't nearly as weak as you'd expect from a bottom-of-the-range CPU, and if you don't run intensive applications the single core isn't the end of the world. If you have an old AM2+ motherboard lying around, it's an ultra-cheap way to build a second PC for web browsing.
Remember, though, that just $50 more will get you a far more capable Athlon II.
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