Upgrading your CPU has never been cheaper, and there's never been as much choice, from single cores, through dual and tri-core parts, all the way to quads. Sounds easy, and when it comes to CPUs it usually is. But still, there's quite a few interesting deals out there, especially if you're building a cheap office/home machine.

Let's start in the gutter, as cheap as it gets. We were considering skipping single-cores altogether, as for just a few euro more you can get a dual-core, and it makes almost no sense to get a single-core these days. However, there's still a market for them; otherwise, they wouldn't be still out there.

Intel's offer is quite limited, and the cheapest Celerons are still Prescott-based, and the cheapest Conroe-based part, the 430, costs €29 and has a low TDP of just 35W. AMD, on the other hand, still has quite a few single-cores to offer. The Sempron 64 LE-1150 at 2.00GHz is the cheapest of the lot. It costs just €16 and has a TDP of 45W.

Moving on to dual-cores, we'll take a look at several price segments, and start cheap, as usual. AMD sells its Athlon X2 4200 at 2.2GHz for €31, while Intel's closest competitor is the Celeron E1200 at 1.6GHz, priced at €38. With such low prices I'm beginning to think dropping single-cores from this roundup was indeed a good idea, but never mind.

Clearly, the low end is still AMD's turf. There's no point in mentioning Intel's oveclocking prowess, as most of these CPUs will end up stuck in cheap, integrated motherboards, and AMD also has an edge when it comes to chipsets in the low end.

However, if we take a look at the rest of the sub-€100 offer, Intel brushes AMD aside, mainly thanks to its cheap E2xxx and E5xxx series parts. You can get an E2000 at 2.2GHz for just €48, or an E5200 at 2.5GHz for €63. Quite good value for the money, and both are overclockable.

AMD recently took a swing at Intel with its new K10-based Athlon X2 7750 Black Edition, clocked at 2.7GHz and priced at €69. You may say this is nothing more than a futile gesture of defiance, but the new CPU offers quite good value for the money, price-wise it sits between Intel's E5200 and E5300, and it offers good performance, albeit it has a rather high TDP. The rest of the dual-core market is dominated by Intel's 45nm parts, and AMD simply has nothing to compete. While AMD's top dual-cores sell for €70, Intel's pricey E8600 at 3.33GHz costs a whopping €219.

At a much more sensible €94 you can get an E7200 clocked at 2.53GHz, or an E8200 at 2.67GHz for €131. Frankly, investing more than €130-€140 in a dual-core CPU doesn't make much sense these days, as at these prices you can already start looking at quads.

Oh wait, I forgot those pesky tri-cores, or three-cores as AMD calls them. Basically these are crippled quad Phenoms. Apart from being cheap, they seem to have another purpose: making AMD feel good about itself, as the tri-core market is currently the only CPU market segment in which AMD reigns supreme. This probably has something to do with the fact that Intel doesn't have any tri-cores of its own, but never mind. At €75, the cheapest Phenom X3 8450 clocked at 2.1GHz does sound like a good deal, but people who don't need CPU muscle get higher clocked, overclockable dual-cores, anyway.

Four-core and seven years ago, Intel and AMD fought a great war, and then AMD launched the Phenom, which was tantamount to raising the white flag. From the start it was clear the 65nm K10 wouldn't be a match for Intel's 65nm quads, let alone 45nm parts, but at least it was cheaper. Unfortunately, that didn't help much, either, as it was only slightly cheaper, but much worse in terms of performance. The cheapest quad-core on the market is AMD's AMD Phenom X4 9550 clocked at 2.2GHz. It costs €106, 40 percent less than Intel's cheapest quad. However, Intel's cheapest quad-core, the Q8200, is a 45nm part clocked at 2.33GHz, not to mention that it can easily attain clocks the Phenom can only dream about. The Q8200 is probably the best choice when it comes to quads in general. The price premium for higher clocked models is huge, and in most cases unjustified. You can still find Kentsfield 65nm parts, but going 45nm is a better choice, and the Q8200 or Q9300 should suffice for most users.

Core i7? At these prices, only the 920 at €241 is worth considering, and the fact that you'll have to get a new, pricey board and memory drives the total transition cost sky high. However, the best choice is to wait for prices to drop.

Phenom II? It's still not out, so it shouldn't be in this roundup, but let's give AMD a break; they've had a tough year, make that two years. Well, the Phenom II looks good. It won't be able to match Core i7 performance, but it will end up much cheaper, and the boards and memory are dirt cheap. However, even when it launches in January, AMD won't have a fast, 45nm dual-core to take on Intel in the lucrative mainstream market.