Understanding AMD CPU Naming
Current AMD CPUs
AMD currently has two marketing names for its desktop and notebook CPUs: Phenom and Athlon. Phenom is the high end marketing name and Athlon the mainstream name.
Both names are used for a great variety of products. An individual product is specified by adding an indicator for the number of processing cores, e.g. X2 or X4. Additionally, there is a product number that currently ranges from 245 and the like up to 1100 with a postfix T for some products.
This may sound confusing, but should become clear in a moment. For a quick reference you may be interested in the budget CPU list.
Athlon Mainstream CPUs
The mainstream Athlon CPUs have no L3 cache, which makes them cheaper to produce, but slightly less powerful than the Phenom CPUs. The current generation of Athlon processors is the Athlon II generation. This is reflected in product names, but is less important, since even leaving the II out the name is unique.
The dual core Athlons are the low end from AMD. The product numbers are in the 200s, like for example the Athlon II X2 255, which is a good entry level CPU. These are good for surfing the internet or office work. They can be had for as little as $50, which is very competitive.
The triple cores are unique to AMD. They currently occupy the 400s in the numbering scheme. An example is the Athlon II X3 455, which is perhaps the best budget gaming CPU out there. Available for $75 to $90 the Athlon X3 series is excellent value that Intel hasn't countered.
Quad core Athlon X4 series is the "quads for masses" offering, which likewise is something Intel does not have. The Athlon II X4 640 is a good balance and available around $100. Any budget video enthusiast should definitely consider.
Phenom High End
Phenom II is the current brand for AMDs high mainstream and high end CPUs. These range from two up to six processing cores with a sizable L3 cache. Despite higher pricing than Athlons, they are still well worth the budget label when you compare to Intel and their up to $1000 SKUs.
Phenom II X2 555 is the current dual core king in AMD's lineup. Excellent gaming performance for a price in the vicinity of Athlon X4.
The triple core Phenom II X3 series is currently restricted to OEMs, but you may see this in a prebuilt off-the-shelf computer. A balance of overall performance and low cost makes it attractive. Numbering in the 700s.
Quad cores center around the Phenom II X4 955 BE, which was the flagship a year or so back. This is excellent performance even by today's standards for a price around $150.
Hexa cores with six processing cores are the latest offering with PHenom II X6 1100T the current flagship. Available for a massive discount compared to Intel's hexas, these are good for hard code video encoding and other parallel apps. Gamers are better served by the higher clocked X4 series.