Athlon is known as the present flagship of AMD for desktop processors, which extends from the single-core models of the older age to the multi-core processors of the newer age. When it comes to the Phenom, it is a newer line of processors made by AMD, which are basically multi-core.
One major factor that makes the difference between the older Athlon and the newer Phenom is the presence of an additional L3 cache in the Phenom processors. This is considered to be larger than both the usual L1 and L2 caches in Athlons, and it enables better performance of the processor.
Phenom also enables an improvement in performance due to its main memory. While Athlons utilize just 800 MHz DDR2 modules, Phenom supports 1066 MHz DDR2 modules, and it won’t throttle down. In addition, Phenom makes use of Dual Dynamic Power Management, while Athlons don’t. And Phenom is well known to consume more power than Athlons.