AMD released its first Phenom II processors, the quad-core "Deneb" CPUs, in January 2009. Triple-core X3 processors (whose performance falls between that of their dual-core and quad-core cousins) followed. Arriving a few months later was the 3.0GHz X4 945 processor, which brought full AM3-socket support. The benefit of this design is that AM3 will allow you to stick DDR3 memory in your system.
This $140 quad-core chip runs a mere 7 percent slower on our WorldBench 6 tests than AMD's top-shelf, six-core Phenom II X6 1090T. The chips have similarities, the X6 is akin to an X4-class processor with two extra cores bolted on. Both share 6MB of L3 cache and run on a 2GHz HyperTransport architecture (the AMD analog to Intel's QPI), but the X6 1090T runs at 3.2GHz, with automatic overclocking up to 3.6GHz. On Cinebench, the six-core X6 1090T outperforms the quad-core X4 945 by 60 percent.
If multithreaded applications aren't your deal, AMD's Phenom II X4 945 is a powerful alternative to its top-shelf Phenom II X6 1090T processor.