Before we render a conclusion, let's have a look at the overall benchmark results:
Because we had no X4 640 at hand, we just reduced the multiplier by 0.5x to get results. As you can see the X4 645 is just 1.7% faster then it's 100MHz slower counterpart.
Nowadays we have an odd situation at least in Europe. Memory prices are below sublevels, with just 40€ per 4GB kit, but Intel CPU prices have increased while AMD has reduced its prices. An 890GX board is available for about €77, while an H55 board costs around €80. The 4850 1GB card is still available for just 77€ which is not a bad deal. If you are not into overclocking AMD gives you the best bang for your buck, but when you do love to overclock Intel can keep up with the costs while the overclocked CPUs proved to be more power efficient. Also, the 890GX onboard graphics are superior the onboard graphics solution from Intel at least up to the H55 generation.
The flagship Phenom II X6 1100T is not a cheap CPU but considering its six cores and the overall good performance, the €199,75 price tag doesn't soud bad, either. We could manage 4GHz with our sample which is also pretty good, but as the benches show, an overclock to 3.85GHz on our 1055T sample manages to come close to the 4GHz result despite the 150MHz less clock due to higher memory and Hypertransport clocks. Depanding what you want to do, the Phenom II X6 is good choice but the 1100T comes with a price premium.
The new Phenom II X4 840 is of course not a Phenom. It's just an Athlon II X4 650 but suprisingly it's cheaper than the 100MHz slower clocked X4 645. At just €90,- it's clearly a bargain. Of course we always state an AMD is not as fast as an Intel CPU because nobody cares to optimize the code for AMD besides Microsoft, but for everyday work and gaming it's a great CPU and AMD does support its sockets much longer than Intel, so it's more future proof.
When planning a new system, investing more in a good graphics card is always better compared to a slightly faster CPU. The Athlon II X4 650 aka Phenom II X4 840 is our recommandation for consumers on a tight budget.
AMD Phenom II X4 840